You don't become infected by gas "particles," but by viruses and bacteria.
Can the viruses and cooties not ride on those particles, the same way when they're ejected high speed out your nasal passage when you sneeze like like a buffalo.
In the case of gases, of which flatulence is composed, the "particles" are molecules, not droplets, many, many times smaller than a virus or cootie.
Methane molecules are 1000x smaller than the virus.
Asserting that an N95 filters a fart is an IQ test.
There is NO MASK certified as effective against bioaerosols.
The ONLY mask rated for biological pathogens is - as opposed to “certified” - merely rated as “meeting CDC guidelines” for Mycobacterium tuberculosis [TB]...a bacterium 20-40x larger than CoV. That’s for 3M’s ‘surgical N95’. Look it up.
If you believe in the “science” of ‘diffusion’, then wear an N95.
But one simple fact flies in the face of N95 effectiveness against viral bioaerosols in the nanometer range:
If N95 was so effective, it would be used in BSL3 laboratories.
They are NOT.
Get exposed, get immune.