Share thisLet’s recap some of the points covered in Part 1:
- The BMBL gives very little guidance to the appropriate level of BSL-3 containment barrier integrity, sparsely stating: (the laboratory) “surfaces should be sealed” and “openings should be capable of being sealed to facilitate space decontamination.” In addition, there are no criteria for verifying that these conditions have been achieved in the BMBL or in any official certification checklist for BSL-3.
- Methods to validate the air leakage of a containment boundary can be classified into two main categories: qualitative and quantitative. The only quantitative test prescribed in the U.S. and Canada is the Pressure Decay Test. However, the Pressure Decay Test is simply not well suited for BSL-3 performance validation.
- Without a relevant quantitative test to use, the most common methods of testing BSL-3 barriers are qualitative tests designed to find holes in the barrier and fix them. That is pretty sound logic overall, but the devil is in the details and in how you record those details in the course of a construction project.
- The two most common methods of identifying air leaks are smoke testing and soap bubble testing. Regrettably, there is no guidance or consensus on what parameters should be used to perform these tests. You have to define them yourself on the basis of laboratory operations and failure scenarios.
Now let’s move onto a discussion of recording test data, defining integrity testing, and some thoughts on developing a test standard using approaches developed in Australia and New Zealand.
Recording Test Data
An important issue with qualitative testing is the witnessing and recording of the data; there’s a lot of it and it can become expensive to record if you want quality assurance. Who witnesses it—besides the contractor or the commissioning agent performing the testing? Is every penetration and every joint in every room tested and witnessed or do you use a smaller random set of rooms and conditions, expanding if the results aren’t conclusive? How are the test results recorded: by notation and/or by video documentation for quality assurance and reference later? Are only failures and retests that pass recorded by video or is everything recorded? The answer is that there is no one method of documentation; it will depend on the size of your facility, the extent of testing, your budget, and your need of the information for licensing and future maintenance/operations plans.
In my opinion, the soap bubble test can be a more efficient method to pretest and witness a room test pass or fail, but you have to contend with a mess to clean up afterward, albeit a very clean mess.
You must define up front, in the test protocol and construction specifications, what you will expect and will accept as remedial action when you find leaks (this issue is irrespective of whether the test is quantitative or qualitative). If you test there will be leaks and the constructor will want to take the easiest route to fix them and move on. You want to ensure that they do not apply quick fixes that will not last over time, do not meet the design intent for airtight assemblies, and generally do not meet the standard of quality construction that you’ve specified and are paying for. As a general rule, where wet sealant (caulking) is the method for sealing openings, then more of it applied properly is perfectly fine, so long as it meets with the manufacturer’s instructions and project specifications for quantity and application. (In general, wet sealant should be white or at least a color, never clear, so it is easy to inspect the material after installation and periodically afterwards. We don’t want the material blending in.) But where the assembly—such as an equipment bioseal with gaskets and overlapping finishes as an airtight solution— does not pass a leak test, then the supplier/installer should re-install the assembly to work as it is meant to.
This brings up the issue of component testing. General expanses of walls, ceilings, or floors do not fail leak tests. Things penetrating through them and where material x joins material y most often do. It is a good thing to check the installation of these penetrations and joints as they are installed as construction quality assurance and timing of remedial work. It is easier to reinstall a box or wall seal before the component is covered up and finishes are done. However, it is difficult to isolate components under differential pressure to do a pre-final validation test when the room is not complete and sealable. It is done on projects that are large enough to warrant the cost of the additional isolation and pressure testing measures. These measures don’t have to be elaborate; all you need is a modified cover plate and hand pump to test the integrity of all electrical junction boxes.Alot of time and project risk is eliminated at the final commissioning phase when you are confident your barrier components have been tested and passed already.
‘Why Test’ Tells You ‘How to Test’
There are many reasons why we want to test barriers, but the most important reason for the facility owner/operator is construction quality. Constructors will naturally take additional care and incorporate better quality assurance measures to ensure they will be able to pass a barrier acceptance test.They have to manage their risk and there’s a lot of risk if they get to the end of a project and find out they’ve not built the laboratory correctly. You can cover up problems that are going to be subjected to visual inspection, but you can’t hide leaks when the room is examined with a smoke pencil or soap solution under negative pressure.My own experience has been dramatically different dealing with constructors,with even the simplest test plan in place. You will know that your containment spaces are built well and should degrade less over time.
Clearly defined integrity testing makes for fairer contracts and better results. There is no ambiguity between contactor and owner when there is a defined,measurable pass/fail test specified for a system. An owner states what is needed, pays for it, and the contractor demonstrates that it is delivered. Simple. Measurable tests are tremendous incentives for quality control. There is no hiding steps missed or corners cut when you crank the air pressure down or up and see the room cannot hold pressure.
Because there is no standard air leakage test for BSL-3 laboratories, I recommend at this time qualitative testing, soap bubble or smoke, at a pressure difference great enough to assure your lab will hold gases for fumigation. For me that is at least 0.2”WC(50 Pa) pressure differential,which will not damage any type of construction but will identify significant leaks. I would readily go to more negative test pressures where I had to ensure that fumigants will not escape out of the room into laboratories or other adjacent spaces operating under negative pressure. Testing at 0.8”WC(200 Pa) or greater is not unreasonable. The greater the pressure differential the more leakage points will be identified. By sealing these failure points, the more airtight your final barrier will be. Depending on the construction type there is a limit to the pressure you should test at (and need to in order to validate that your room is capable of fumigation). I recommend that 2”WC (500 Pa) differential pressure is the most negative that a room should be tested at. More negative pressures have the potential to damage construction.