Breathing apparatus
A breathing apparatus was a type of personal life support system that allowed an individual to breathe their own form of air while in an alien atmosphere. 

Some Benzites were unable to breathe a standard oxygen/nitrogen atmosphere, and therefore had to wear a breathing apparatus in those environments during the early 2360s. By the early 2370s, this device had largely fallen into disuse, though at least one Benzite serving in Starfleet still employed a breathing apparatus in 2380. (; ; , et al.)

In 2370, Jadzia Dax recalled the story of a hydrogen-breathing Lothra and an Oxygene who fell in love and yet could only be in the same room for forty minutes a day without their breathing apparatus, nonetheless staying together for fifty-seven years. She gave Melora Pazlar this example to convince her that a relationship with Julian Bashir wouldn't be impossible, despite the differences between them. ()

Types of breathing apparatuses 
 Breather
 Breathing mask
 Breathing tube
 Filter mask
 Inhaler
 Respirator

External link 
 

de:Respirator
Life support technology