Abreathing mask is used for keeping harmful particles from entering the respiratory system, and when inhaled, the particles lodge in the respiratory system, causing or aggravating health problems. Given these facts, a breathing mask keeps what from being inhaled and causing health problems among the following options:
- cigarettes
 - harmful particles
 - chemical changes
 - influenza
 - oxygen particles
 - hydrogen and oxygen
 - air particles
 - atmosphere particles


 

  harmful particles       