âI got the impression listening to the podcast that directional airflow, and a differential pressure gradient were critical safety measures even todayâ, not just in BSL-3 labs, but more broadly. Alison said:
The airflow issue is a problem that comes up over time. One of the things I think thatâs important for listeners to understand is that one of the main ways that labs try to keep these pathogens from infecting people outside the lab is to control the airflow in the labs: they operate under whatâs supposed to be negative air pressure. And this lab [at the Birmingham Medical School; I do not think it was BSL-3 nor BSL-4] had problems with airflow, allowing particulates to float out into areas where people would not have been thinking they were at risk of becoming infected.
Theyâre talking about Janet Parkerâs infection in 1978, right? That was before the introduction of the BSL system, and controls were very lax compared to today. Among other things, the rooms werenât anywhere close to airtight, which made negative pressure much more important. I see this inclusion in the interview as an illustration of why airflow controls are important.
Note also that when Young talks about controlling air flow sheâs talking about something much broader than directional airflow. That also includes things like biosafety cabinets and positive pressure suits, and I donât think anyone is saying these arenât critical tools?
I think the above is in tension with Alison seemingly highlighting the importance of a differential pressure gradient in CDCâs BSL-3 lab
I donât think these are in tension? The Bennet study is talking about how to design BSL-3 labs, and Young is describing a situation where a CDC lab wasnât being operated as designed. It reads to me like after an accident the CDC labâs airflow management wasnât operational at all. This would still have been be a serious issue if the lab had been designed along Bennetâs recommendations, focusing on inflow velocity.
Overall it looks to me like Young is trying to give a high level introduction to biosafety, including giving specific examples of historical failures to explain why you care how the air is flowing. Then youâre responding by citing papers that say âbetter to manage airflow this way and not this wayâ as if they conflict with her explanations, but I donât actually see conflicts?
Overall it looks to me like Young is trying to give a high level introduction to biosafety, including giving specific examples of historical failures to explain why you care how the air is flowing. Then youâre responding by citing papers that say âbetter to manage airflow this way and not this wayâ as if they conflict with her explanations, but I donât actually see conflicts?
Fair! The post was supposed to be a little bit of a call to being curious and controlling for a thinkerâs big idea rather than confidently pointing to conflicts. It is also worth noting that optimal number of biosafety failures (and maybe even pandemics?) is not 0. As Bryan Caplan said:
Whenever there is a disaster, the normal reaction is, âSomething has to be done to stop this from ever happening again.â Again, the question is: Maybe we should just stay the course, because this is the right number of disasters to have? Which horrifies people. But look, we shouldnât have earthquake codes so strict that no building ever collapses, no matter what, because the effect on housing costs would be astronomical. So why donât you tell me what is the correct number of houses to collapse in earthquakes [or airflow issues in biosafety labs]? And then weâre only going to cover it in the media if we exceed that number. You just imagine peopleâs heads exploding, like, âNo, we have to cover every single one so that we can have the proper reaction!â This proper reaction is what makes housing costs too high.
Of course, it still makes sense to be aware of the risks, and I think it is great that Alison has contributed to that! I have added the above quotation and sentences before and after it in this comment to the post.
Below are some quick replies to the other parts of your comment, but I wanted to say the above 1st because for me it is the most important part.
Note also that when Young talks about controlling air flow sheâs talking about something much broader than directional airflow. That also includes things like biosafety cabinets and positive pressure suits, and I donât think anyone is saying these arenât critical tools?
I have not looked into that, but I guess they are important.
I donât think these are in tension? The Bennet study is talking about how to design BSL-3 labs, and Young is describing a situation where a CDC lab wasnât being operated as designed. It reads to me like after an accident the CDC labâs airflow management wasnât operational at all. This would still have been be a serious issue if the lab had been designed along Bennetâs recommendations, focusing on inflow velocity.
Right, directional airflow should have been working, but Alison also seemed to imply there is a need for a differential pressure gradient, which is in tension with Kurth 2022 saying:
Only a 2005 study by (Bennett et al.,2005) addresses the relationship between negative pressure and protection from cross-contamination in BSL-3 laboratories in an evidence-based manner and concludes that pressure differentials has no effect on protection from cross-contamination.
Theyâre talking about Janet Parkerâs infection in 1978, right? That was before the introduction of the BSL system, and controls were very lax compared to today. Among other things, the rooms werenât anywhere close to airtight, which made negative pressure much more important. I see this inclusion in the interview as an illustration of why airflow controls are important.
Note also that when Young talks about controlling air flow sheâs talking about something much broader than directional airflow. That also includes things like biosafety cabinets and positive pressure suits, and I donât think anyone is saying these arenât critical tools?
I donât think these are in tension? The Bennet study is talking about how to design BSL-3 labs, and Young is describing a situation where a CDC lab wasnât being operated as designed. It reads to me like after an accident the CDC labâs airflow management wasnât operational at all. This would still have been be a serious issue if the lab had been designed along Bennetâs recommendations, focusing on inflow velocity.
Overall it looks to me like Young is trying to give a high level introduction to biosafety, including giving specific examples of historical failures to explain why you care how the air is flowing. Then youâre responding by citing papers that say âbetter to manage airflow this way and not this wayâ as if they conflict with her explanations, but I donât actually see conflicts?
Fair! The post was supposed to be a little bit of a call to being curious and controlling for a thinkerâs big idea rather than confidently pointing to conflicts. It is also worth noting that optimal number of biosafety failures (and maybe even pandemics?) is not 0. As Bryan Caplan said:
Of course, it still makes sense to be aware of the risks, and I think it is great that Alison has contributed to that! I have added the above quotation and sentences before and after it in this comment to the post.
Below are some quick replies to the other parts of your comment, but I wanted to say the above 1st because for me it is the most important part.
Right.
I have not looked into that, but I guess they are important.
Right, directional airflow should have been working, but Alison also seemed to imply there is a need for a differential pressure gradient, which is in tension with Kurth 2022 saying: