Pressure decay testing is a systematic procedure to validate room construction to determine if the laboratory’s containment barrier defined by walls, floors, ceilings, penetrations, and other construction features meet the required integrity to prevent leakage of unfiltered air from the BSL-4 containment space. Pressure decay testing is the most reliable method to prove that a BSL-4 laboratory room’s envelope is airtight. The National Institutes of Health, which oversees the operation of the BSL-4 laboratories located in Fort Detrick, Maryland, and Hamilton, Montana, indicates that the standard BSL-4 pressure testing method is to negatively pressurize the room to 2 InH2O, and then measure the pressure decay. The requirement for a BSL-4 laboratory is to maintain a pressure higher than 1 InH2O after 20 minutes (Memarzadeh, 2009). This quantifiable test can pinpoint issues with critical equipment in a BSL-4 laboratory including:
Pressure decay testing provides an acceptable level of quality for annual verification testing of BSL-3 Ag and BSL-4 laboratories. The complex design and operation of these facilities minimize the potential risk of an aerosolized pathogen to staff, the general population, and the surrounding environment. The pressure decay test verifies that there is no air leakage. Air leakage can compromise research studies through cross-contamination of multiple pathogens.
The following steps must occur before conducting a pressure decay test:
The room passes the pressure decay test if the residual pressure at the end of the 20-minute period is -1.00 InH2O or more negative (50% of the initial room’s pressure value) under steady state conditions for temperature and barometric pressure. Each pressure zone within maximum containment (BSL-4) must pass two consecutive pressure decay tests.
If annual pressure decay testing is not feasible for some rooms, then another option would be conducting a smoke saturation test. A smoke saturation test is a qualitative test, but it will help the users to identify possible issues with the containment envelope. The maximum containment engineering/maintenance team will need to command the laboratory into maintenance or decontamination mode. The surrounding areas will be more negative; therefore, if there is a leak or issue during the testing, the maximum containment team will be able to identify it. The challenge with this method is that it is only recommended if the rooms are decontaminated.
Another option (a little bit messy and more time-consuming) is the use of a soap solution on critical areas. This test is the least accurate option because it will only test perimeter barrier components. The laboratory will require decontamination prior to testing.
If there is a decontamination or maintenance mode for the facility, you can run what we call a “light pressure decay test.” Before a decontamination process begins, you need to make sure the laboratory is airtight. The light pressure decay test is typically conducted from the BAS for testing and running trends. No additional testing equipment is used. This is a non-invasive procedure.
BSL-3 laboratories can be pressure decay tested depending on the laboratory’s envelope construction system, calculated room’s leakage rate, and room’s isolation capabilities. Pressure decay testing on BSL-3 laboratories is more challenging since, by concept, these types of laboratories are considered “leaky labs” (infiltration of air is required). However, with the implementation of good room isolation standard operating procedures, the pressure decay test can be achieved with no issues.
Pressure decay testing is a team effort. Our recommendations to have a successful pressure decay test include:
If you would like to learn more about pressure decay testing, contact World BioHazTec for a free consultation or send us an email.
Farhad Memarzadeh (2009, September 15). Pressure and Temperature Correction for BSL4-Pressure Decay Test. (O. o. National Institutes of Health, Producer) Retrieved 2023, from Pressure and Temperature Correction for BSL4-Pressure Decay Test: https://orf.od.nih.gov/TechnicalResources/Bioenvironmental/Documents/PressureandTemperatureCorrectionforBSL4_508.pdf