Notes from the biosafety level 3 lab


And now for something completely different – I thought I would write a bit about my job. If you’re not interested in science you can skip this bit!

I started writing this from inside a biosafety level three facility (BSL3) during a week when I was in there almost constantly. At the time I had some incubation periods in my experiment protocol, and it was not worth it to go in and out of the facility for such short time periods (nor is it recommended – leaving means changing out of my biosafety outfit into normal clothes, which means taking off a whole lot of things which must then be laundered or thrown away and then replaced the next time I come back in). Normally when we are inside, we try to stay in for as long as possible, so a day in there usually means one break for lunch. Before we go in we try to make sure we have eaten, drunk something and been to the bathroom, so that we do not need to leave again – normally when we get out it’s hard to know what to do first, drink (working in there leaves you feeling quite dehydrated), use the bathroom or eat!


So what is biosafety level three?

Bascially there are four biosafety levels in laboratories.

Biosafety level 1 is a normal lab, where you work with bioorganisms that are harmless or present minimal risk to immunocompetent individuals. It’s recommended to wear gloves and a labcoat and experimental waste must be disposed of in a safe way.

Biosafety level 2 is required for pathogens that pose a moderate risk because they may cause disease if you accidentally inject yourself or swallow them but are treatable and not airborne. Here you also have to wear a labcoat and gloves, access to the lab is restricted, and special training is required in how to work safely.

Biosafety level 3 is used for airborne pathogens that can cause serious or potentially lethal disease for which treatment is available, such as Mycobacterium tuberculosis. For this you have to wear a more complex outfit, which I will explain in a minute, the labs have a special negative air pressure system, and all work with the infectious agent is performed inside a protective cabinet (hood). Special training is required to work in a BSL3 lab, since there are particular procedures to working with the infectious material.

The highest level, Biosafety level 4, is for working with extremely dangerous and potentially fatal pathogens such as Ebola and others for which there is no reliable treatment. The protective equipment for working here is at an even higher level, and people either wear the “spacesuits” that you see in the movies, with a separate air supply, or work in special cabinets.

We are working on tuberculosis in our BSL3 lab, so the only time we have to wear the “spacesuit” is when we are using a machine to sort cells, which creates aerosols. For the rest of the time, we do everything under the hood. We enter our laboratory through a special room (anteroom) in which we change from our clothes into our BSL3 outfit.


We keep our own underwear, and on top of that goes a shirt and pants (basically the same as hospital scrubs), and on top of that a light-coloured gown with a solid front closed with ties or press-studs for easy removal. The light colour of labcoats and these gowns is so that you can easily notice if you have dropped something on yourself. We also put on lab socks and shoes, and in the lab where we work with higher concentrations of Mtb we put on shoe covers as well – in this lab we spray our shoes with disinfectant after each use and they never leave the lab (they are also regularly washed with stronger disinfectant).

We put on two pairs of gloves: first one pair, which we tape with thick tape to the gown so that there is no skin open to the environment – and then the second pair on top. In some labs they wear oversleeves instead of taping the gloves, but taping the gloves is a good idea as it ensures that nothing can roll up, leaving your skin exposed (perhaps in some labs they even do both). We also wear a hair cover and a mask with a special filter: FFP2 masks for normal work and FFP3 if we are doing unfixed flow cytometry (which could also create aerosols) or working with clinical strains.

Working in a BSL3 lab requires learning special techniques. For example, you must always change your outer gloves when removing your hands from underneath the hood, which means careful planning, as you cannot just put your hands in and out to fetch things that you may need. Before you start, you have to set the hood up so that everything you need is there and arranged in a way that makes it easy to work and avoids cross-contamination of items. It’s good to keep a “clean” portion of the hood, where you can place things once you have disinfected them after use. A beaker with disinfectant and a cloth is always kept inside the hood, and you frequently clean the surface of the hood, and also clean items that are to be removed from the hood. You can see now why two pairs of gloves are important, as even after removing the “dirty” pair of gloves, you still have a protective layer on your skin. There is even a special technique for removing gloves to prevent you contaminating your skin in the process.

All items used inside the hood are stored inside plastic boxes, and only opened inside the hood or at the airflow – the box is only opened by clean gloves and the items inside are only touched with gloves that go inside the hood. This means that it’s helpful to work with someone, since one person can open the box and the other person can remove the items inside and put them in the hood. If you work by yourself, you have to open the box, remove the lid and place it on the air flow, then remove the things inside, then change your gloves to close the box. Needless to say, you go through a lot of gloves this way, even if you use the two-handed method, where you keep one hand out and clean and only change one glove. However it’s always necessary to work by yourself sometimes, so you organize things to be as efficient as possible, lining up things to remove all together instead of going in and out of the hood fifty times.

Because you are always focused on keeping things clean and safe, it does take some concentration to work in the BSL3 lab. You need the right kind of personality to work there – high-strung, impatient people who rush or get stressed easily should not work in a BSL3 laboratory, as they are likely to make mistakes. You have to just be calm and patient, and accept that things will take as long as they take. And if things go wrong and you drop a whole lot of infectious bacteria on the floor (for example), you shouldn’t panic but just follow the procedures you have been taught for dealing with such situations.

More often that situations like that are just silly annoyances. For example, the other day I had just got out of the S3 and changed back into my normal clothes when I realized that I had forgotten to turn the air conditioning back on in one room. That meant re-entering the S3, i.e. changing back out of my clothes into S3 clothes and then back again when I came out a minute later!

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