* Polluted environments:
industrial zones, or places affected by dust from construction sites.
* Allergy seasons: During spring and fall when pollen and other allergens are abundant in the air
restaurants (in non - smoking sections that may still have some smoke drift), or areas where people are smoking outdoors,
* Some industrial settings: In certain workplaces where there are low - level chemical fumes or dust, like in some laboratories,
woodworking shops, or light manufacturing facilities
industrial environments, specialized respirators are usually required.