Glossary of Terms | Retrotec

Looking for the definition of a particular phrase or acronym? Here are some of the most common terms used in the airtightness testing industry:

Agent/Air Interface

See sharp interface – the vertical distance through which the agent concentration goes from that discharged to 0.

AHJ

Authority Having Jurisdiction.

ASHRAE

The American Society of Heating, Refrigerating and Air Conditioning Engineers. Developers of standards and technical guidance relating to HVAC/R issues.

BCLA (Below Ceiling Leakage Area)

Leaks below a suspended ceiling. Hole in the floor or lower leaks. Often assumed to be one half of the Total Hole in the Room (ELA).

Below Ceiling Leakage

See Lower Leak.

Blower

As used in the text, this term means the Retrotec fan unit that both flows air and provides a flow pressure signal from which flow is measured.

Ceiling neutralization

See Flex-Duct Test

Center Panel

A red ABS plastic molded sheet, which goes between the upper and lower panel to fill the gap.

Conditioned Space

An area or volume that is normally air-conditioned or heated (i.e. inside the thermal envelope). Even though supply ducts may not discharge directly into these spaces, they are conditioned if their temperature follows indoor temperature closer than outdoor.

Continual Mixing

Airflow activity within the test room that is sufficient to maintain an equal concentration at all locations and prevent the formation of distinct zones of air and agent/air mixture, i.e. no interface develops.

Continuous Discharge

See Extended Discharge.

Descending Interface

Agent leaks out during the retention period and air leaks in the upper part of the enclosure to replace the lost volume. Typically it is assumed that as the agent leaks out, an interface will occur between the layer of agent on the bottom and the layer of air on top. Since this interface drops with time, it is called a descending interface and is the most commonly assumed leakage regime. The other regime is Continual Mixing.

Depressurization

The process of creating a negative pressure in the enclosure by blowing air out of it.  Air is drawn in from outside to replace it, showing up as “geysers” when checked with an air current tester.

Door Fan

A test instrument that fits into an open doorway in order to pressurize or depressurize an enclosure. A Door Fan is often called a Blower Door or an Infiltrometer™.

Dropped Ceiling

See suspended ceiling.

Dynamic discharge pressure

This is a combination of the peak pressure during the actual discharge and the velocity pressure associated with streams of agent hitting walls or ceilings, thereby trying to force its way out of the enclosure during this brief period.

Enclosure

In this manual, this word is used to mean the volume that is protected with clean agent. It could also mean the above ceiling space if it is not protected since for all intents the enclosure boundary is at the fire barrier and suspended ceilings do not represent a fire barrier unless they are fitted with special fire rated tiles.

Envelope

The surfaces composed of floor and walls and floors that separate the test volume from volume surrounding the test volume

Equivalent Leakage Area (ELA)

In layman’s terms, the ELA is the size of hole we’d have if all the building’s cracks and holes could somehow be brought together. Also called: Whole Room Leakage and includes Leaks through the ceiling and below the ceiling (BCLA). In CA2001 we measure this in units of sq.ft. or sq.m. at a reference pressure in Pascals (Pa). In Engineer’s terms: the equivalent size of hole required in a flat plate to give the same flow rate having a discharge coefficient of 0.61 and taken at the Reference Pressure. This ELA is sometimes called the EqLA or Canadian ELA because it was first used in the Canadian GSB air leakage standard for houses. This ELA enjoys worldwide acceptance by most testers, even in the US. This ELA should not be confused with another ELA that is often called the EfLA or Effective Leakage Area. It is very unfortunate that both these ELA’s have the same acronym of ELA. The EfLA was developed for the US ASTM Standard and is smaller than the EqLA by at least a factor of 0.61 because it uses a discharge coefficient of 1.0. This EfLA is sometimes called the LBL or Lawrence Berkley Labs ELA because it was developed there and is used in the LBL natural airchange model that enjoys wide usage- apart from that usage, the EfLA is not used very much but the existence of both can cause confusion - be sure to know which you need.

Expander Mechanism

The mechanism of knobs and levers attached to the door panel that enables the panel system to expand sideways into the door frame.

Extended Discharge

An optional method to maintain concentration whereby after the initial discharge an extended discharge takes place with the intention of maintaining the original concentration more or less by injecting a continuous stream of agent for an extended period (usually 10 to 20 minutes). Retrotec CA2001 software will calculate the amount of extended discharge required. An Extended Discharge is sometimes called Continuous Discharge.

Extender Panel

An optional molded plastic panel, which can be temporarily attached to the main door panel to fit up to 48” wide doorways.

False Ceiling

See suspended ceiling.  Also, can be called T-bar ceiling or Lay-in ceiling.

Flex-duct Ceiling Neutralization

A door-fan test method that uses a second fan connected through the suspended ceiling. The second fan takes care of the upper room leaks with the above the ceiling fan. The first door fan takes care of the Lower Leaks.  The flow through both door fans is adjusted till there is neutral flow across the ceiling that is verified by smoke puffed into gaps. The Lower fan measures the Lower Leaks.

Flow Pressure

The pressure difference between inside the door fan and the surrounding air read from channel B on the DM-2 or the Infiltrometer’s™ 60 and 250 Pa flow gauges.  It is used by the computer to calculate the airflow through the blower.

Height of Interest

The highest point in the room requiring protection for the duration of the specified retention time. In the NFPA procedure it’s called the “height of interface from floor”, in the software it’s called the Minimum Protected Height.

Hole in Floor (BCLA)

All Below Ceiling Leakage Area (BCLA) is assumed to be in the floor to get worst-case leakage rate.

HVAC

Heating Ventilating and Air conditioning system.

Infiltrometer

A name used and registered by Retrotec to describe their door fan equipment. Often called blower door.

Large or Main Panel

Refers to the panel with the 20” diameter hole intended for sealing the doorway.

Lay In (Tile) Ceiling

See Suspended Ceiling.

Leakage

A general term used to describe holes or the area of holes or leakage through holes in or around an enclosure. See also Total Leaks and Lower Leak(s).

Leakage Area

This is the same as “Leakage” but express in sq.ft. or sq.m.

Lower Leak

A lower leak is any leak below the ceiling. Leaks in the walls and floor are counted as Lower leaks where agent will leak out. Lower Leak also refers to the Lower Leak tab of CA2001 where the Lower Leak would be measured.

Lower Leaks

Leaks attributed to air that flows in from below. If the room were filled full of water, more water would leak from these leaks. All leaks below the ceiling are assumed to be Lower Leaks. Includes wall and floor leaks.

Negative Static Pressure

A room pressure that is independent of the door fan that will cause test smoke to flow into the room.

Pascal (Pa)

Often shown as “Pa”. A very small metric unit of pressure. There are 249 Pascals in 1” Water Column (the pressure required to push water up 1” in a tube). One Pascal = 0.000145 psi.

Peak Pressure

When the system is discharged, there is brief period at the ten-second mark where a maximum peak pressure is created in the room. For inerts, this is where the flow rate is near maximum. For halocarbons this occurs at the end of the discharge where the cooling effect of the agent is reduced and it starts to expand. CO2 starts to increase in volume towards the end of the discharge because the cooling effect caused by the rapid flashing of the agent at the nozzles is eliminated.

Peak Pressure is sometimes called Vent Pressure.

Positive Static Pressure

A room pressure that is independent of the door fan that will cause test smoke to flow out of the room.

Pressurization

This is the process of creating a positive pressure in the house by blowing air into the enclosure.  Air is pushed out through all the leaks, causing the smoke to move away from the operator when checked with an air current tester.

Protected enclosure

This term describes the total space that is flooded with clean agent upon discharge.  This includes above ceiling spaces only if that volume is intentionally flooded with agent.  This includes adjacent rooms if they are discharged at the same time.

Protected enclosure boundary

This term describes floor, wall and surfaces that define the protected enclosure.

Reading

A set of simultaneous Room Pressure and Flow Pressure readings.  Sometimes referred to as a data set or test point because it is plotted as one point on a graph.

Reference Pressure

The pressure at which the ELA is calculated, usually at the test pressure.

Return Path Space (Relief Zone)

The volume around the tested room that the door fan blows into (under room depressurization) or out of (under room pressurization).  The flow from the door fan must be allowed to return to the point of leakage in the room through the return path space.

Room

See Enclosure.

Room Pressure

The pressure difference created by the door fan between inside and outside of the enclosure.  This pressure is commonly measured by channel A on the DM-2 or off of the Infiltrometer 60 Pa gauge.

Sharp Interface

The height at which the agent concentration is considered to go form that discharged to 0. The boundary between the agent mixture below and the pure air above.

Smaller Panel

Refers to the smaller sliding panel used to seal the doorway. It’s permanently attached to the large panel.

Suspended Ceiling

Common ceiling type found in most computer rooms and offices.  Tiles lift up to expose space above.

Total Leaks

Total Leak includes floor, wall and ceiling leaks. It also refers to the Total Leak tab in CA2001 where the total leak is measured.

T-bar Ceiling

See Suspended Ceiling.

Upper Panel Cover

This covers the 22” diameter hole (20” for the older 900 series models) in the upper panel and has 2-calibration holes cut to precise size at the factory. The panel comes out with a quick pull.

Upper Leaks

Leaks attributed to air that flows in from above. If the room was filled full of water, no water would leak from these leaks. Also called the Hole in the Ceiling.

Vent Pressure

See Peak Pressure.

Whole Room Leakage (ELA)

See Total Leaks.