the GNU version of the Collaborative International Dictionary of English
adj. Suitable for being breathed; adapted for respiration.
The Century Dictionary and Cyclopedia
That can respire.
Capable of or fit for being respired or breathed: as, respirable air.
Word Usage
""This will be the first major advancement in monitoring miners' exposure to respirable coal dust," said Ed Thimons , branch chief for dust control, ventilation and toxic substances at NIOSH."