These days the dangers of smoking causing cancers is well known. Many jurisdictions recognise smoke as causing some cancers in firefighters.
Cancers take a while to develop but smoke can kill with one exposure.
Small smoke particles of 2.5 micron (called PM2.5) and smaller than that are dangerous.
These get deep in the lungs, change the chemical composition of blood and may cause heart attack, which happens to be the greatest cause of death for wildfire fighters worldwide.
The Fair Air mask removes all PM2.5 particulates and 99.94% of PM0.3, about the size of Coronavirus.
Real respiratory protection.