Just to put some numbers on this, we can assume that burning wood has plenty of particles in the 0.2-0.3 micron range, which is commonly regarded as “the most penetrating particle size”.
In the following study, the better of the surgical masks that was studied allowed 25% of the 0.3 micron particles through, which matches the 1/5th effectiveness you mentioned. https://www.cdc.gov/niosh/nioshtic-2/00210276.html
On p16 of this EPA handout, they absolutely do mention the hand-holding logic of having a false sense of security. But they also address the possibility that the mask can make breathing more difficult, contribute to heat stress, and that these masks:
do not filter out harmful irritant gases, such as acrolein or formaldehyde, or other toxic gases, such as carbon monoxide
They also specifically state:
Masks can also be used in conjunction with other methods of exposure reduction, including staying indoors, reducing activity, and using HEPA air cleaners to reduce overall smoke exposure.
So I think the serious answers to your final questions are: it would help by 25%, I sure as hell would, and maybe?
Just to put some numbers on this, we can assume that burning wood has plenty of particles in the 0.2-0.3 micron range, which is commonly regarded as “the most penetrating particle size”.
N95 masks meet the standard that they filter out 95% of these particles. https://www.cdc.gov/niosh/nioshtic-2/20023155.html
In the following study, the better of the surgical masks that was studied allowed 25% of the 0.3 micron particles through, which matches the 1/5th effectiveness you mentioned. https://www.cdc.gov/niosh/nioshtic-2/00210276.html
On p16 of this EPA handout, they absolutely do mention the hand-holding logic of having a false sense of security. But they also address the possibility that the mask can make breathing more difficult, contribute to heat stress, and that these masks:
They also specifically state:
So I think the serious answers to your final questions are: it would help by 25%, I sure as hell would, and maybe?