AABC (Associated Air Balance Council)
AABC is an organization that sets standards for independent testing, adjusting, and balancing (TAB). AABC members must meet strict independence and competency requirements.
Plain-language definitions for HVAC testing, adjusting and balancing (TAB), hydronic balancing, and critical room concepts used in our reports.
Tip: Search for terms found in your TAB report, inspector requests, or commissioning specs.
AABC is an organization that sets standards for independent testing, adjusting, and balancing (TAB). AABC members must meet strict independence and competency requirements.
AABC standards defining TAB procedures, tolerances, and reporting expectations.
Acceptance is the formal approval that systems meet design intent and all major deficiencies are resolved.
Acceptance criteria are the rules that define what ‘passing’ looks like. This can include airflow tolerances, pressure targets, temperatures, control responses, or room pressure relationships.
Acceptance testing is the final set of inspections and measurements required to confirm that systems meet the specified requirements before turnover.
How close a measurement is to the true value.
ACH is the number of times the air inside a room is replaced with new or cleaned air every hour.
Air changes per hour at 50 Pa during a blower door test (tightness metric).
Sealant used on duct seams/penetrations to prevent sound leakage.
Adjusting is making controlled changes to move the system toward design intent. Examples include trimming balancing dampers, setting valve positions, or changing fan/pump speeds (where permitted).
The affinity laws describe how changes in fan or pump speed affect flow, pressure, and power.
A measure of how long air has been in a space; used for ventilation effectiveness.
Association with standardized performance ratings for HVAC equipment.
Certification that equipment meets stated performance ratings.
An AHU is the central machine that conditions and moves air through a building. It typically contains filters, heating and cooling coils, fans, dampers, and controls.
A continuous layer system that controls air leakage through the building envelope.
The unbroken connection of air barrier components across transitions and penetrations.
Air changes per hour measure how many times the air volume of a room is replaced every hour.
Measured ACH based on airflow or tracer gas, not just design target.
Envelope leakage normalized by area, used in performance targets.
Noise that increases as duct/terminal velocities are too high for the design.
The use of ventilation, filtration, exhaust, and pressurization to prevent the spread of airborne pathogens.
The volume of air moving through a duct, diffuser, grille, or fan. Common units are CFM (cubic feet per minute) and L/s (litres per second). In rooms, airflow balance compares how much air is supplied versus exhausted/returned.
An airflow station measures real-time CFM using multiple pressure taps and a built-in DP transducer.
Notification triggered by a point/state outside normal limits.
A BAS alarm is triggered when a value goes out of range or equipment fails to respond. Common alarms include high static pressure, low airflow, high humidity, or valve position faults.
Threshold at which an alarm occurs (distinct from control setpoint).
Alarm thresholds define sensor readings that trigger alerts—for example, low room pressure or high CO₂.
Association with fan performance/arrangement standards and ratings.
Program certifying fan performance data used for design and selection.
An analog output is a BAS signal (often 0–10V or 4–20mA) that adjusts equipment such as valves, dampers, and VFDs.
The ante room supports handwashing, garbing, and air cleanliness transition between uncontrolled areas and cleanrooms.
An anteroom is a small buffer space between a critical room and a corridor. It helps stabilize pressure and provides a place for staff to enter, exit, and perform gowning or doffing.
A defined interface used for data integration between software systems.
Drawings updated to represent the actual installed system configuration.
As-found means the measured condition before any adjustments are made. It shows how the system was operating when we arrived on site.
Instrument condition before adjustment; shows drift since last calibration.
ASHRAE is a global standards body that publishes ventilation, refrigeration, and HVAC design requirements used throughout the industry.
Safety standard for refrigeration systems (machinery rooms, refrigerant limits).
ASHRAE 170 is the ventilation standard for healthcare facilities. It defines supply, exhaust, ACH, and pressure relationships for different room types.
Healthcare ventilation standard frequently cited for ACH, pressure, filtration, and airflow direction.
Refrigerant safety classification standard (A1, A2L, B2, etc.).
Thermal comfort standard defining acceptable indoor environmental conditions.
ASHRAE 62.1 defines minimum ventilation rates and IAQ requirements for commercial buildings. It guides how much outdoor air is needed per person and per area.
Residential ventilation and IAQ standard (useful when working in multi-unit buildings).
Energy standard for buildings covering HVAC efficiencies and required controls/commissioning features.
Commissioning guideline defining commissioning process requirements and terminology.
HVAC&R technical commissioning guideline (methods and documentation).
As-left means the measured condition after adjustments are completed. It is the final recorded result at the time of reporting.
Instrument condition after adjustment; shows compliance at return-to-service.
Standard test method for building airtightness by fan pressurization (multi-point).
Standard test method for determining air leakage rate by fan pressurization (envelope).
An automatic balancing valve maintains a preset flow despite pressure changes in the system.
A multi-port pitot that averages velocity pressure across a duct.
Open building automation protocol used for devices and BAS communication.
BACnet carried over RS-485 serial networks.
A standardized data structure (e.g., Analog Input) representing a point.
A BACnet point is a data variable in the BAS—such as temperature, damper position, or static pressure—broadcast over BACnet protocol.
BACnet carried over Ethernet/IP networks.
Balancing means proportioning air or water so each branch, zone, or terminal gets the correct share. It’s not just ‘more or less’—it’s getting the distribution right across the system.
A balancing valve is a device used to manually trim or set water flow in hydronic systems. It helps ensure each coil gets its correct design flow.
A BAS is a centralized control and monitoring system for HVAC, lighting, pressures, and other building systems.
Connecting HVAC equipment controls into a central BAS for monitoring and control.
A baseline is the reference condition you compare against. In TAB and audits, the baseline is often the as-found condition or the design intent, depending on what you are trying to prove.
The Basis of Design explains the engineering decisions and assumptions that support the design intent.
Serial communication speed setting; must match across devices on a bus.
BACnet Broadcast Management Device; helps BACnet/IP broadcasts cross subnets.
Fan tone frequency = RPM × number of blades; common tonal noise source.
A fan test that pressurizes/depressurizes a building to measure leakage.
A branch duct carries air from the trunk duct to diffusers, grilles, or terminal units.
Noise that escapes through duct walls into a space.
Noise spread across many frequencies (often turbulence related).
A BSC is a ventilated hood that protects staff, the product, and the environment during hazardous drug or biohazard work.
A buffer room is an ISO-classified cleanroom that houses the PEC used for sterile drug compounding.
Building pressurization is the overall pressure balance between the inside of the building and outdoors. It is controlled by how much outdoor air, return air, and exhaust air the systems move.
Air that bypasses intended coils/filters or occupied zones due to leakage or poor damper geometry.
Calibration is the process of comparing an instrument to a known reference and adjusting or documenting its accuracy.
Planned frequency for recalibration (e.g., annually) based on risk/usage.
Attachment that helps a flow hood capture supply air more completely.
Air velocity needed at a hood/opening to capture a contaminant plume.
Cavitation occurs when water vapor bubbles form and collapse inside a pump, causing noise and damage to the impeller.
CFM measures how much air moves through an outlet or duct each minute. TAB reports compare measured CFM to design values.
Reversal of combustion exhaust due to negative pressure in the building.
A circuit setter is a calibrated balancing valve used to measure and control water flow through coils or branches.
A cleanroom is a controlled environment where airborne particles, temperature, humidity, and pressure are regulated to protect products and patients.
CO₂ levels indicate how well a space is ventilated relative to occupancy. Higher CO₂ means insufficient fresh air.
A CO₂ sensor measures carbon dioxide concentration to reflect occupancy and ventilation effectiveness.
Codes are enforceable laws or regulations that govern building safety, ventilation, equipment installation, and mechanical systems.
A coil bypass allows a portion of water to flow around the coil rather than through it. It is sometimes used for control stability or freeze protection.
Commissioning is the structured process of verifying that building systems are designed, installed, tested, and operating as intended.
The lead party responsible for planning and managing the commissioning process.
Post-install checks to confirm noise targets in critical/quiet spaces.
A commissioning plan outlines what systems will be tested, how they will be verified, and what documentation is required for acceptance.
Final summary of commissioning scope, tests, results, issues, and acceptance.
Plan showing when startup, TAB, functional tests, and turnover deliverables occur.
The project spec section that defines commissioning scope, roles, and deliverables.
Owner, designers, contractors, TAB, and Cx provider who execute commissioning activities.
How well individual suites/rooms resist air leakage to adjacent spaces.
A compounding room is a pharmacy space where medications are prepared, often with specific airflow, filtration, and pressure requirements to protect both products and staff.
Likelihood that surfaces fall below dew point, causing moisture and mold potential.
A tracer gas test that injects at a constant rate to calculate airflow from steady concentration.
Containment refers to controlling hazardous materials so they do not escape the designated handling area.
Contamination control ensures airborne contaminants do not escape or enter a critical space by managing ventilation, filtration, and pressure relationships.
A control damper moves automatically to regulate airflow as commanded by the building automation system (BAS).
Adjusting control parameters (e.g., PID gains) so a loop reaches setpoint quickly without hunting or overshoot.
A control valve modulates water flow through a coil based on temperature or demand. It opens and closes gradually to regulate heating or cooling output.
A cooling coil uses chilled water or refrigerant to remove heat and moisture from air passing through it.
COP measures the ratio of heating or cooling output to electrical energy input. A COP of 3 means 3 units of heating per unit of electricity.
Corrective action is the work performed to resolve a deficiency—such as repairing a damper, fixing a sensor, adjusting controls, cleaning a coil, or correcting duct/piping issues.
Using airflow offsets to keep corridors positive/negative relative to adjacent rooms.
BACnet feature that reports point changes without constant polling.
A C-PEC is a PEC designed for hazardous drug compounding, providing containment and ISO 5 air.
The component/section causing the largest pressure loss and limiting flow.
A critical room monitor displays differential pressure and may trigger alarms when the room loses its required pressurization.
Unwanted airflow that disrupts capture (e.g., supply diffuser blowing across a hood).
Sound transmission between rooms through ducts/ceiling plenums.
CSA publishes safety and performance standards used in Canadian building, electrical, and mechanical systems.
CSA Z317 outlines requirements for HVAC systems in Canadian healthcare facilities, including ventilation, pressurization, and system reliability.
Canadian standard for special requirements for HVAC in health care facilities.
A C-SEC is the room surrounding the C-PEC, designed to maintain negative pressure relative to adjacent spaces.
Serial bus wiring topology where devices connect in a line (preferred for RS-485).
A damper is a movable plate inside a duct or opening that controls how much air can pass through.
How much a damper’s pressure drop dominates its branch, affecting controllability.
Device/software that records measurements over time for analysis.
A-weighted decibel level used to rate noise as perceived by humans.
Deadband is the range where the BAS avoids heating or cooling to prevent rapid cycling. Example: 21°C to 24°C.
The decoupler is a short pipe connecting primary and secondary loops, allowing water to bypass coils or boilers if flows do not match.
A deficiency is a documented issue where equipment or systems fail to meet design or performance requirements.
A record of deficiencies discovered during commissioning and verification.
Deliverables are the outputs you receive—usually the TAB report, deficiency list, summary tables, and any requested data sheets or verification forms.
DCV adjusts ventilation rates using CO₂ or occupancy sensors to reduce excessive outdoor air when spaces are under-occupied.
DCV adjusts ventilation rates based on occupancy or CO₂ levels to save energy while maintaining IAQ.
Correcting airflow/energy calculations for temperature/pressure/altitude.
The design intent describes how the building systems are meant to perform, including airflow rates, temperatures, and controls logic.
A design standard is a document that outlines how systems must be designed or sized. Standards are not always legally mandatory, but they guide engineering decisions.
Unique ID on a network/bus used to route communication.
The temperature at which moisture condenses; used to assess wall/duct sweating risk.
Dewpoint is the temperature at which air becomes saturated with moisture and condensation begins.
A DP sensor measures the pressure difference between two points, commonly used for isolation rooms and coil pressure drops.
Sensor that outputs ΔP for filters, coils, room pressure, or flow devices.
A diffuser is a supply air outlet that spreads air evenly into a room, usually from the ceiling. It mixes supply air with room air for comfort and proper ventilation.
A digital manometer measures pressure differences, often very small ones, in inches of water column or Pascals.
Directional airflow is the intended main direction that air moves between spaces, such as from a corridor into a negative room, or from a positive room into a corridor.
Expected non-coincident peak load/flow used to size systems (not all zones call at once).
Documentation control refers to managing changes, revisions, and traceability of TAB reports, drawings, tests, and commissioning records.
The gap at the bottom of a door that allows transfer air to pass between spaces. The size of this gap strongly affects room pressurization.
Door undercut is the gap under a door, and door seals are gaskets at the edges. Together they form a controlled leakage path that allows air to move while limiting drafts and noise.
Air passing under doors; often a dominant intentional/unintentional transfer path.
Door usage or door cycling describes how often doors into a critical space are opened and closed and how long they stay open each time.
How opening doors changes pressure and airflow, often revealing marginal designs.
Ultrasonic flow meter that uses reflections from particles/bubbles; needs a “dirty” fluid.
Differential pressure is the difference in pressure between two spaces, usually measured in Pascals or inches of water.
A draft is a localized feeling of moving air across the skin, often caused by poorly aimed diffusers or unbalanced airflow.
Slow change in instrument output over time under constant input.
Duct leakage is unintended air escaping from holes, seams, or weak joints in ductwork.
Acoustic/thermal lining inside ductwork to reduce noise and condensation.
Pressurizing duct sections to quantify leakage at a target pressure.
Practical concept: reduce velocity, add liner/attenuator, fix vibration and fittings.
Duct sealing uses mastic, tape, or gasketed joints to prevent leakage of supply or return air.
A duct traverse is a method of measuring airflow by taking multiple pressure readings across a duct using a pitot tube or similar probe and then calculating average velocity and airflow.
Ductwork is the network of metal or flexible passages that distribute air throughout a building.
An economizer increases outdoor air intake when the outdoor conditions are cool enough to provide 'free cooling' without using mechanical cooling.
Economizer control determines how much outdoor air the system uses for free cooling based on temperature or enthalpy conditions.
Economizer lockout disables free cooling when outdoor conditions are unsuitable, such as too warm or too humid.
EER measures the cooling efficiency of HVAC equipment at a specific outdoor temperature, typically 95°F (35°C).
An eggcrate grille is a high-free-area return grille made of intersecting bars. It allows large amounts of air to pass with low resistance.
An elbow is a duct fitting that turns airflow, typically 45° or 90°, with inside radius affecting pressure drop.
Pressure control impacts airflow up shafts and can affect lobbies and corridors.
Verifying how HVAC behaves during fire alarm, smoke control, or emergency sequences.
Energy efficiency is the ability of HVAC systems to deliver heating, cooling, or ventilation using the least amount of energy possible.
Energy recovery systems capture heat or humidity from exhaust air to reduce the energy needed to condition incoming outdoor air.
Total heat content of air (sensible + latent) used for coil/energy checks.
Verification of air/water/vapor control layers via testing and inspection.
Manufacturer sound ratings used for design and compliance checks.
Single equivalent hole sizes representing leakage through many cracks/openings.
An ERV transfers heat and moisture between outgoing and incoming air streams to reduce ventilation energy costs.
Indoor air leaking out through envelope leaks (often carrying moisture).
An exhaust fan removes air from washrooms, labs, isolation rooms, or other spaces and discharges it to the outdoors.
Face velocity is the speed of air passing through a grille or diffuser opening, measured in feet per minute (FPM).
Average velocity across a hood/filter face used for performance checks.
Testing performed at the factory to verify equipment functionality before shipment.
The fail position is the state equipment moves to when power or control signals are lost. For example, dampers may be spring-open or spring-closed.
Fan energy is the electrical power consumed by supply, return, or exhaust fans as they move air through the system.
Fan speed determines how much air a fan moves. Speed may be fixed, belt-driven, or controlled by a VFD.
A fan-powered box includes a small fan to draw in plenum air and mix it with supply air before delivering it to the zone.
FDD uses algorithms or BAS logic to detect abnormal HVAC operation, such as stuck dampers or excessive fan energy.
FGI publishes design guidelines for healthcare facilities, including ventilation, room function, and environmental conditions.
Facility Guidelines Institute requirements influencing healthcare ventilation and design.
A field calibration check is a quick test to confirm an instrument is behaving reasonably, such as comparing two meters or checking zero and span.
Quick check against a reference to confirm an instrument is still reasonable.
Filters remove dust, particles, and contaminants from air before it enters occupied spaces.
A filter bank is a section of an AHU that holds multiple filters arranged in stages or arrays.
The set of signals/interlocks between the fire alarm system and HVAC (shutdown, smoke control, damper position, etc.).
Network rules controlling allowed traffic; can break BAS comms if misconfigured.
An indirect route sound takes around barriers (e.g., through ceiling voids).
Canvas/fabric connection to reduce vibration transmission at duct connections.
Flexible duct is a lightweight, spiral-wound duct used primarily for small branch connections.
Parameter describing leakage flow through an opening in power-law models.
A multi-sensor array that measures duct velocity profile and outputs airflow.
A flow hood is a box-shaped device placed over a diffuser or grille to directly measure the airflow coming through that outlet.
Adjustment applied to a hood/box to improve accuracy for a diffuser type.
Using theatrical fog to visualize room air patterns and short-circuiting.
Friction loss is the pressure loss caused by water moving through pipes, fittings, valves, and coils.
Friction rate represents the pressure loss per unit length of ductwork, used to size ducts properly.
An FPT is a documented test that simulates real operating conditions to ensure system performance meets the design intent.
Defined acceptance criteria used to objectively judge a functional test outcome.
Functional testing verifies that systems respond correctly to controls, setpoints, alarms, and operating conditions.
Device/software translating between protocols when systems aren’t natively compatible.
A globe valve is a type of control valve commonly used in hydronics because it provides precise modulation and good control authority.
GPM measures the amount of water flowing through a pipe or coil. It is the primary unit of flow for hydronic balancing.
Operator screens showing equipment status, values, and controls.
A grille is an opening through which air returns or exhausts from a room. Grilles do not spread air—they simply allow airflow into ductwork.
Testing a portion of a building while guarding adjacent zones to isolate leakage.
A guideline provides recommended best practices rather than enforceable rules. Many healthcare and ventilation requirements come from guidelines.
Local control mode selection; impacts commissioning and control behavior.
Head is the pressure energy a pump adds to the system, typically measured in feet of head.
A heat exchanger transfers heat between two isolated water loops, such as between boiler water and building water.
Heat load is the amount of heat a space gains from occupants, equipment, lighting, and sunlight.
Heat transfer is the movement of heat from one place to another—such as from chilled water into warm air, or hot water into cold air.
A heating coil warms air using hot water, steam, or electric elements to maintain space temperature.
A coil is a heat exchanger inside an air handling unit or fan coil. Hot or cold water runs through the coil, transferring heat to or from the air.
A HEPA filter removes 99.97% of particles at 0.3 microns, used in cleanrooms, PECs, and isolation rooms.
A high alarm is triggered when a monitored value exceeds the acceptable upper limit.
High-frequency noise often from high-velocity air or leakage.
Database/system optimized for storing and querying time-series building data.
A hot-wire anemometer measures air velocity at a point using a heated sensor. It is often used at grilles, in ducts, and in critical spaces.
Concept: sensitive at low velocity but can be affected by turbulence and temperature.
An HRV transfers heat (but not moisture) between exhaust and outdoor air, reducing heating and cooling load.
A humidity sensor measures the amount of moisture in the air, providing RH or dewpoint values.
Hunting occurs when a control loop continuously overshoots and corrects itself, causing rapid oscillations in temperature, pressure, or airflow.
A hydronic system circulates water through pipes to deliver heating or cooling to coils, radiators, and other equipment.
Different outputs for the same input depending on whether input is rising or falling.
List of physical inputs/outputs and their wiring/points used for checkout.
Indoor Air Quality refers to the condition of air inside a building, including contaminants, humidity, odours, and ventilation levels.
International Energy Conservation Code; a common energy code benchmark (often referenced in specs).
Induction is the process where fast-moving supply air pulls room air along with it, helping mix and distribute air evenly.
Heavy base used under equipment to improve vibration isolation performance.
Uncontrolled outdoor air entering through leaks due to pressure differences.
Rotational flow entering a fan that reduces measured airflow and increases noise/vibration.
How much a silencer/attenuator reduces sound through it.
Functional test that verifies multiple systems (HVAC, fire, BAS, power) work together.
Confirming required device interactions (e.g., fan proves on before damper opens).
Air leakage between rooms through walls, ceilings, doors, and penetrations.
Network addresses (IPv4/IPv6) used for BACnet/IP devices and BAS servers.
IPAC refers to guidelines and best practices that minimize the spread of infections in healthcare facilities, including HVAC-related requirements for isolation and protective environments.
Protocol framework for energy measurement and verification methods.
Cleanroom suite of standards for air cleanliness and testing in controlled environments.
Defines cleanroom ISO particle concentration classes (e.g., ISO 7, ISO 8).
Test methods for cleanrooms (airflow, particle counts, recovery, etc.).
ISO classes define the level of particle cleanliness in a space, with ISO 5 being cleaner than ISO 7 or ISO 8.
An isolation room is a patient space designed to control the spread of airborne contaminants by using specific airflow, air change, and pressure relationships relative to surrounding areas.
Central list of commissioning issues, statuses, owners, and closeout evidence.
A calibration constant converting measured velocity pressure to airflow for a flow station.
A LAFW provides ISO 5 laminar airflow for sterile non-hazardous drug preparation.
Latent load refers to the moisture content in air that must be removed or added to maintain humidity.
Air leakage around pipes/cables/shafts due to unsealed penetrations.
Leakage class describes how much air a duct leaks relative to its surface area, measured in CFM per 100 square feet at a reference pressure.
A leakage path is any unintended opening where air can move between spaces, such as cracks around doors, ceiling penetrations, or unsealed wall openings.
The physical route air takes through gaps (door undercuts, ceiling voids, shafts).
Green building credit requiring expanded commissioning scope and documentation.
Limitations describe constraints that affect testing or balancing—like restricted access, equipment not operating in the intended mode, incomplete controls, or missing documentation.
A linear bar grille is a rectangular or continuous grille with fixed bars. It can be used for supply or return depending on the duct arrangement.
How closely sensor output follows a straight-line input/output relationship.
Load reduction refers to strategies that reduce heating or cooling demand on HVAC systems.
A low alarm is triggered when a monitored value drops below the acceptable lower limit.
LPM is the metric version of water flow. Some Canadian projects list both GPM and LPM.
A Magnehelic gauge is an analog dial instrument mounted on walls or panels to show differential pressure, often across filters or between rooms and corridors.
Water flow meter based on electromagnetic induction; requires conductive fluid.
When exhaust exceeds makeup air, driving the building negative.
Process to confirm energy performance outcomes against a baseline (often IPMVP-based).
Measurement uncertainty describes the expected range of possible error in a reading due to instrument limits, setup, and conditions.
The MERV rating indicates how effectively a filter removes particles of different sizes. Higher MERV values capture smaller particles.
Mixed air is the blend of outdoor air and return air inside an AHU. The mixed-air damper controls the proportions.
Common industrial protocol used to integrate meters, drives, and packaged equipment.
Modbus over serial RS-485.
Modbus over Ethernet/IP.
Using ongoing monitoring and analytics to continuously verify and optimize performance.
Lightweight messaging protocol used for IoT telemetry; sometimes used for analytics.
A Make-Up Air Unit provides outdoor air to replace air removed by exhaust systems, such as kitchens, labs, or large washroom groups.
Model code used as a basis for provincial building codes across Canada.
Meeting the project’s specified background noise target.
NEBB publishes standards and certifies firms for TAB, commissioning, and building systems testing. NEBB and AABC are the two primary TAB standards in North America.
Standards and best practices for TAB and commissioning documentation.
The neck is the opening behind a diffuser where the duct connects. Its size affects airflow and pressure drop.
A room is negatively pressurized when its air pressure is lower than surrounding spaces, drawing air inward.
A negative pressure room is kept at a slightly lower pressure than adjacent areas so air flows into the room when doors open. This helps keep contaminants from escaping to surrounding areas.
A simple rubber isolation pad (limited low-frequency performance).
A portion of network separated for performance/security/reliability.
Height in a building where indoor and outdoor pressure are equal (stack effect).
Life Safety Code; egress and smoke compartment concepts can impact HVAC zoning.
Standard for air-conditioning and ventilation systems (fire/smoke considerations).
Standard related to smoke control systems (design and testing concepts).
Healthcare facilities code (gas/essential systems) that can affect ventilation risks.
General term for smoke control design/testing requirements (e.g., stair pressurization).
Calibration traceable to a recognized national standard chain.
A rating method using NC curves to judge acceptable background noise.
A non-conformance is a failure to meet a design, specification, or code requirement.
NPSH is the minimum pressure required at a pump’s inlet to prevent cavitation.
Operations and maintenance manuals used for turnover and long-term operations.
Unique number identifying a BACnet object in a device.
Occupied mode runs HVAC equipment at normal ventilation and temperature conditions. Unoccupied mode reduces airflow, temperature, or equipment operation to save energy.
Frequency grouping used to analyze HVAC noise by tone ranges.
Odour issues occur when contaminants, insufficient ventilation, or pressure imbalance cause smells to linger or migrate.
Continuous process of maintaining and improving system performance over time.
Provincial building code that governs many HVAC and life safety requirements in Ontario.
Industrial interoperability standard sometimes used for BAS/data integration.
The O&M manual includes equipment data, maintenance procedures, and control sequences required to operate the building.
BAS workstation used by operators; commissioning confirms usability and graphics.
Outdoor air is fresh air brought into the HVAC system for ventilation and dilution of contaminants.
Forcing a point/value temporarily for testing or troubleshooting.
Document stating what the owner needs the building/systems to do; the north star for commissioning.
Part-load efficiency describes how well equipment performs under partial load conditions, which represent most real-world operation.
A PEC is a controlled work device—such as a biological safety cabinet or isolator—providing a clean environment for compounding.
A PICV maintains constant design flow through a coil regardless of pressure fluctuations in the hydronic system. It also acts as a control valve.
Isolating piping supports to reduce structure-borne vibration/noise.
A pitot tube is a probe that measures both static and total pressure in a moving airstream so velocity pressure and airflow can be calculated.
Coefficient used to account for probe characteristics in velocity calculations.
A plenum is an open airspace used to move air instead of ductwork, such as a ceiling cavity used as a return pathway.
Room-to-room sound transfer through shared ceiling plenum and return paths.
Supply/return mixing or transfer through a ceiling plenum that defeats room pressure intent.
Standardized naming so points are searchable and consistent across graphics/trends.
Verification that each physical I/O and software point is mapped and working.
Confirming sensors/actuators are wired, addressed, and reading correctly in BAS.
BAS requesting point values on a schedule (as opposed to event-based reporting).
A room is positively pressurized when its air pressure is higher than adjacent spaces, forcing clean air outwards.
A positive pressure room is kept at a slightly higher pressure than adjacent areas so air flows out of the room when doors open. This helps protect the room from contaminants entering.
Model describing airflow through leaks: Q = C × ΔP^n.
How repeatable measurements are under the same conditions.
A Pre-Functional Checklist confirms that equipment is installed correctly and ready for functional performance testing.
A pressure cascade is the stepwise arrangement of pressure differences between rooms to control contamination movement.
Confirming a multi-room pressure hierarchy holds under realistic door states.
Pressure differential is the measurable difference in pressure between two adjacent spaces.
Pressure drop is the reduction in pressure as air or water moves through filters, coils, or long ducts due to friction and resistance.
Planned pressure losses through components used to verify design vs field performance.
Parameter describing how leakage flow changes with pressure (power-law exponent).
Damper that opens to relieve excess building pressure and prevent door issues.
A pressure setpoint is the target room pressure difference that the control system is trying to maintain between a critical room and its reference space, such as the corridor.
A pressure transducer converts air or water pressure into an electrical signal for monitoring or control.
Pressurization is the control of room or building pressure by adjusting supply, return, and exhaust airflow.
Primary/secondary pumping uses separate pump loops connected by a decoupler to prevent pumps from fighting each other.
A primary–secondary system separates the main plant loop (primary) from the building distribution loop (secondary) using closely spaced tees or a decoupler so flows do not interfere with each other.
A defined language/rule set used for devices to communicate (BACnet, Modbus, etc.).
Graph of air properties used to analyze humidity, enthalpy, and processes.
A pump moves water through a hydronic system, overcoming friction in pipes, fittings, coils, and valves.
A pump curve shows how flow (GPM) changes with head (pressure) for a given pump and speed.
A punchlist is the list of outstanding deficiencies or incomplete items that must be corrected before project closeout.
Minimum to maximum measurable value of an instrument.
Recommissioning applies the commissioning process to an existing building to correct performance drift and restore design operation.
Commissioning again after changes, drift, or major operational issues (distinct from initial Cx).
Recovery time is how long it takes a room to return to its intended pressure and airflow conditions after being disturbed, such as after a door opening or system change.
Field markups used to create as-builts (often collected during commissioning).
Noise created by airflow turbulence at fittings, dampers, and terminals.
A register is a supply outlet with a built-in damper, commonly used in residential HVAC systems.
A reheat coil warms the air after it leaves a VAV box to maintain zone temperature without increasing airflow.
Relative humidity is the percentage of moisture in the air compared to the maximum it can hold at a given temperature.
Designed path for excess air to leave a zone/building without forcing leakage.
Closeness of repeated readings under identical conditions.
Closeness of readings when conditions/operators/instruments change.
A reset strategy automatically adjusts setpoints such as supply air temperature, duct static pressure, or chilled water temperature based on demand.
Smallest change an instrument can display or detect.
How quickly a sensor responds to a step change in input.
Repeating a failed functional test after corrections are made.
A re-test is a follow-up measurement after changes have been made—such as repairs, control adjustments, or balancing—to confirm results are now acceptable.
Retro-commissioning is a more intensive version of RCx focused on optimizing older buildings with major performance issues.
Commissioning applied to existing buildings that were never commissioned or need recovery.
A return fan pulls air back from rooms into the air handler to be reconditioned or exhausted.
Reverse flow in a decoupler occurs when the secondary loop pulls more water than the primary loop supplies, backfeeding the primary.
Difference between supply and exhaust/return that creates intended room pressure.
The path air takes as it enters, circulates within, and leaves a room. Good airflow patterns remove contaminants effectively.
Room classification refers to the required cleanliness, airflow, pressure, and filtration levels for a specific healthcare space.
A noise rating system emphasizing rumble and hiss characteristics.
A room pressure monitor is a device that continuously measures the pressure difference between a room and a reference space and often provides a visual indicator and alarms.
A room pressure monitor displays the pressure difference between a critical room and adjacent spaces.
Concept: better for higher velocities; poor at low velocity or turbulent flow.
Two-wire serial communication layer used by Modbus RTU and BACnet MS/TP.
Providing bias resistors/idle-state voltage on an RS-485 bus to improve stability and prevent floating signals.
An RTU is a packaged air handling unit placed on the roof. It contains fans, heating/cooling coils or packs, filters, and controls built into one box.
An RTU sensor package includes supply, return, outdoor temp, and enthalpy sensors used for economizer and ventilation control.
Low-frequency noise often from fans, ducts, or vibration.
How frequently data is recorded; affects trending and detection of events.
Scope of work is the agreed list of tasks, systems, and deliverables included in a project. It defines what is included, what is excluded, and what documentation is required.
Functional tests postponed to appropriate weather/load conditions after occupancy.
Seasonal testing verifies equipment that cannot be tested during construction due to out-of-season weather conditions.
SEER measures the seasonal cooling efficiency of air conditioners and heat pumps by comparing cooling output to electrical energy consumed.
Sensible load is the temperature-related heating or cooling required for comfort.
A sensor measures a physical property such as temperature, humidity, pressure, or airflow and sends the data to the building automation system.
Calibration adjusts a sensor to ensure its readings match actual measured values.
Sensor failure occurs when a sensor stops reporting or gives erratic values. Sensor drift is when readings slowly become inaccurate over time.
Translating written sequences into actual implemented logic/points.
The sequence of operations describes exactly how HVAC equipment should behave under different conditions, including start-up, normal operation, alarms, and shutdown.
The Sequence of Operation defines how equipment and control systems respond under various operating conditions.
Setback (cooling) or setup (heating) reduces HVAC output during unoccupied periods to save energy.
A setpoint is the value the BAS tries to maintain, such as temperature, humidity, static pressure, or differential pressure.
Adjusting setpoints to meet OPR while minimizing energy and instability.
Air movement up/down shafts that alters corridor and room pressure balance.
Shop drawings provide detailed fabrication and installation information that supplements design drawings.
When supply air exits to return/exhaust without properly mixing in the occupied zone.
Sign-off is the formal acceptance that work meets the agreed criteria. In practice, this is often based on the final report and verification results.
Testing performed on site to verify installed equipment functionality.
A slot diffuser is a linear supply outlet with one or more narrow openings. It delivers air horizontally along ceilings or walls.
Industry association with duct construction and leakage testing guidance.
Leakage classification approach often used for duct leakage specs and tests.
A space/region with engineered pressure/flow control for smoke management.
Using smoke to identify air leakage points at the envelope.
A handheld tool that releases visible smoke to reveal local airflow direction and turbulence.
A duct component designed to reduce transmitted fan/airflow noise.
Instrument that measures sound pressure level (often dB(A)) for noise surveys and compliance checks.
Using controlled background noise; HVAC must not overpower or conflict.
Sound energy output of a source (equipment rating, independent of distance).
Measured sound level at a location (what occupants hear).
A duct/plenum configuration that blocks sound paths while allowing airflow.
The full-scale measurement range (max minus min).
A specification is a project-specific document that defines what the HVAC system must do, including airflow, temperature, pressure, materials, and testing requirements.
A vibration isolator using steel springs for low-frequency isolation.
Stack effect is the natural upward or downward movement of air in a tall building caused by temperature differences between inside and outside.
Pressure difference caused by indoor/outdoor density differences and building height.
Smoke control strategy keeping stairs positive during fire events.
Serial wiring topology that often causes communication issues on RS-485.
Vendor/contractor documentation showing initial equipment checks and settings.
Static pressure is the pressure in the duct system. AHU fans maintain a duct static setpoint so enough air reaches all terminals.
Pressure exerted by air in a duct not related to velocity.
A map of static pressure at key points through a system to locate restrictions.
Static regain is the increase in static pressure that occurs when air slows down due to an increase in duct size.
Stratification occurs when warm air rises and stays near the ceiling while cooler air remains near the floor due to poor air mixing.
Noise transmitted through building structure rather than air.
A submittal is a document from a contractor providing product data, shop drawings, and performance specifications for approval.
Review of equipment submittals against OPR/BOD and commissioning requirements.
A logical division of an IP network affecting broadcast and routing.
Pressure difference between a suite and corridor/outdoors affecting odors and comfort.
A supply fan pushes conditioned air from the air handler into the duct system and then into rooms.
Loss of fan performance due to poor inlet/outlet conditions (tight elbows, obstructions, swirl).
Curated owner-facing manual describing how systems are intended to operate and be maintained.
TAB is a structured process used to measure HVAC performance, make controlled adjustments, and confirm the system delivers the air and water flows it was designed for. In simple terms: measure → tune → prove it.
A takeoff is the fitting where a branch duct connects to a trunk duct, often with a damper or scoop to direct airflow.
A tee fitting splits air at a 90-degree angle, often causing more turbulence and pressure loss than a wye.
Temperature gradient refers to differences in temperature across different parts of a room or between floor and ceiling.
A temperature probe is used to measure air or water temperature at specific points, such as entering and leaving a coil or within a room.
A temperature sensor measures air or water temperature and provides input to heating and cooling controls.
A terminal unit is any device that controls airflow at the end of a duct system, including VAV boxes, FPBs, and reheat terminals.
When upstream pressure or duct sizing prevents VAV/terminal units from reaching setpoints.
End-of-line resistor required on RS-485 buses to reduce reflections.
A test port (also called a P-T plug) is a small, sealable access point that allows a probe to measure pressure or temperature in a pipe without draining the system.
A test procedure is a step-by-step method describing how measurements are taken so different technicians can produce comparable results.
Step-by-step functional test procedure used to verify sequences and interlocks.
Having owner/Cx witness present during functional tests for acceptance.
Testing is the measurement step—collecting actual field data (airflow, water flow, pressures, temperatures) using instruments. Testing comes before any adjustments are made.
A conductive path through insulation that increases heat loss and can drive condensation.
Infrared imaging to locate insulation gaps and air leakage signatures.
The throw pattern describes how supply air travels from a diffuser before slowing to room velocity.
Keeping device clocks aligned so trend data and alarms have correct timestamps.
Tolerance is the allowed difference between the design value and the measured value. Example: a diffuser designed for 200 CFM might be acceptable within a specified percent range.
Dominant discrete frequency noise (whine) vs broadband noise.
Sum of static and velocity pressure at a point.
A ventilation test where a tracer gas concentration is allowed to decay to estimate air change rate.
Formal training sessions provided to building operators on installed systems.
Transfer air is air that moves between spaces through door gaps, grilles, or intentional openings to maintain pressurization.
A transition changes the duct size or shape—such as rectangular to round or large to small.
A trend log records sensor values over time for analysis of system performance or troubleshooting.
BAS time-series recording for analysis and troubleshooting.
Trend logs allow the BAS to record sensor readings and equipment statuses over time so technicians can diagnose issues.
Using trend logs as a method means intentionally recording and reviewing BAS data over time to understand how systems behave during real operation.
A defined duration of BAS trending used to prove stability and performance.
The trunk duct is the main duct that carries the largest airflow from the air handler before splitting into branch ducts.
Ontario authority for boilers/pressure vessels affecting mechanical rooms and safety.
Collection of final documents: TAB, Cx report, O&M, training, as-builts.
Standard for closure systems for air ducts and connectors (tape/mastic ratings).
Standards for fire dampers and smoke dampers, respectively.
An ultrasonic flow meter measures water flow from outside the pipe by sending sound waves through the pipe wall and timing how they travel with and against the flow.
Ultrasonic setup means entering the correct pipe size, wall thickness, and material into the meter and using proper coupling gel so the sensor can read reliably.
Compounding standards that drive room pressure, ACH, and containment/filtration requirements.
USP 797 defines the environmental and operating requirements for preparing non-hazardous sterile medications.
USP 800 defines environmental requirements for hazardous drug compounding, focusing on containment and staff safety.
Valve authority describes how much of a valve’s pressure drop is available for good control. Poor valve authority leads to unstable temperature control and noisy valves.
A vane anemometer uses a small rotating fan to measure air velocity. It is commonly used at larger grilles and outdoor air intakes.
A material that slows water vapor diffusion; differs from an air barrier.
Variable flow systems use VFD-controlled pumps to adjust water flow based on demand, increasing efficiency.
Variance is the difference between the target (design or required value) and what was measured. It may be shown as a number, a percent, or both.
A VAV box modulates airflow to a zone by adjusting an internal damper, usually under BAS control.
A VAV box is a terminal unit that modulates airflow to a zone using an internal damper under BAS control.
Dynamic pressure related to air velocity (used with pitot).
How well supply air reaches occupants/contaminant sources compared to perfect mixing.
The amount of outdoor air provided to a space or system. Often expressed as L/s per person, L/s per m², or CFM. In healthcare and labs, ventilation rate is commonly described as ACH and/or minimum outdoor air per ASHRAE/FGI requirements.
Verification confirms that work is installed and operating according to plans, specifications, and manufacturer requirements.
How vestibules reduce infiltration by adding an airlock to entrances.
A VFD adjusts motor speed based on load, reducing energy consumption for fans and pumps.
High-frequency motor/drive noise sometimes caused by switching frequencies.
Using mounts/pads/springs to reduce vibration transmission to structure.
VOCs are airborne chemicals released from paints, cleaning products, furnishings, and building materials.
A VOC sensor detects volatile organic compounds that may cause odors and IAQ complaints.
Post-occupancy review near warranty end to catch issues while still covered.
Water flow is the rate at which water travels through piping, coils, and valves. Proper water flow ensures coils can transfer heating or cooling effectively.
Seals around doors/windows that reduce uncontrolled infiltration.
Temperature related to evaporative cooling; used in psychrometrics.
Pressure difference caused by wind speed/direction (positive windward, negative leeward).
A wye splits airflow smoothly into two paths with less turbulence than a tee.
A constant bias where an instrument reads nonzero at zero input.
Setting a differential pressure instrument to zero before measuring.
Mismatch between tracked airflow (BAS) and actual airflow due to sensor/K-factor error.
Finer frequency bands used to identify tones and diagnose sources.
Delta-T is the difference between the entering and leaving water temperature across a coil or heat exchanger.
If you're seeing terms like ACH, pressure cascade, or delta P requirements and need clarity fast, we can review your scope and provide a clear plan.
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