@elilla ​
https://www.harihareswara.net/posts/2023/my-current-covid-risk-approach/

<blockquote>
This P100 has an exhalation valve, which I have <a href="https://www.microcovid.org/blog/masks#modified-p100-respirators">covered up with a piece of KN95 or surgical mask material and some tape</a> so that I am protecting others by filtering my exhalations. I keep meaning to buy <a href="https://www.3m.com/3M/en_US/p/d/v101254496/">the official 3M exhalation valve filter</a> and install it (about USD$10 each but seems to only come in a pack of 6).
</blockquote>