少点错误 05月23日 10:57
Qualitative Fit Testing
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本文探讨了在紧急情况下佩戴弹性体呼吸器的重要性,并介绍了如何测试口罩的密合度。文章分享了作者邀请朋友们尝试不同口罩并进行密合度测试的经验,详细描述了定性密合度测试的流程,包括使用带有强烈味道的颗粒物来检测口罩的密封效果。此外,文章还指出了测试过程中可能遇到的问题,如喷雾器的性能差异,并提供了改进建议。

😷 佩戴弹性体呼吸器在紧急情况下至关重要,因为严重疫情的发生概率较高,即使在保守估计下,投资回报率也可能达到10倍左右。

💨 为了确保口罩有效,需要测试其密合度,因为不合适的口罩会导致空气泄漏。一个简单的测试方法是戴上口罩,感受是否有空气泄漏,或者堵住进气口吸气,看口罩是否紧贴面部。

🧪 定性密合度测试使用带有强烈味道的颗粒物,如糖精或苦味剂,来检测口罩的密封效果。测试者将颗粒物喷洒在头部罩内,如果颗粒物无法穿透口罩,尤其是在头部移动、说话和做鬼脸时,则表明密封良好。

⚠️ 作者在使用测试套件时遇到了问题,特别是两个喷雾器的性能差异。建议在测试前调整喷雾器,确保它们性能一致,以获得更准确的测试结果。

Published on May 23, 2025 2:50 AM GMT

As I wrote about lastweek, it's worth it for everyone to have an elastomeric respiratorin case of emergencies: the chance of a severe pandemic is high enoughthat even under reasonably conservative assumptions the return oninvestment is ~10x. Because not every mask fits every face and apoorly fitting mask will leak air around the seal—it doesn'tmatter how good the filters are if they're bypassed—it's good totry on a range and see what's good. I invited some people over to tryout a range of masks and play with fit testing.

There are a range of ways to see if a mask fits. A good first test isto put it on and see if you feel air leaking around it. If it'spossible to cover the intake you can breath in while wearing it, andyou should feel it pull tight against your face. These tests areoften enough to rule out masks, and are pretty quick.

Once you've identified a mask you think is plausibly a good fit youcan do qualitative fit testing. The idea is, you make some particleswith a strong taste or smell, and see how well they can get in whileyou're wearing the mask. If they can't get in, especially as you moveyour head around, talk, and grimace, then your seal is pretty good. Igot a kit (GersonQLFT50M) which included several components:

You put the liquid in the nebulizer, poke the nebulizer through a holeconveniently provided in the front of the hood, and squeeze outparticles.

One key thing about the setup is there are two solutions and twonebulizers. One is the weaker sensitivity solution, which you breathemaskless to ensure you can detect the test particles, and the other isa stronger [1] test solution, which ideally doesn't make it throughthe mask in detectable quantities.

While this seems to be a common design, I really don't like how itrelies on the two nebulizers performing identically. Especially sinceinitially mine didn't: the sensitivity testing nebulizer worked great(easy to squeeze, you can see the little bubbles going, fine mist)while the fit testing nebulizer worked much less well (harder tosqueeze, needed more adjustment, much less little bubble movement, lessmist). After people went home I played with the nebulizers and got abetter feel for how to adjust them to get them both performing well.This would have been good to do before!

I'm planning to bring the masks and test kit to LessOnline, which I expect to beenriched for people who would be interested in this sort of thing.


[1] You use a muchlarger difference for saccharin (100x in the fit test) than Bitrex(12.5x). I'm still confused about this, but some asking Geminisuggests it's because "the 'low, but generally detectable'concentration and the 'significantly stronger, but not unbearable'concentration are vastly different relative to each other for thesetwo substances due to their intrinsic taste properties."



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口罩 呼吸器 密合度测试 疫情防护
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