Which of the following O2 devices has 2 one-way valves and the second valve is at the exhala-tion ports, which prevents room air from entering the mask during inhalation?

a. Nonrebreathing mask c. Aerosol tracheost-omy collar mask
b. Partial rebreathing mask d. Simple mask

ANS: A
The first set of valves is a one-way valve located between the reservoir bag and the base of the mask. This valve allows gas flow to enter the mask from the reservoir bag when the patient in-hales and prevents gas flow from the mask flowing back into the reservoir bag during the pa-tient's exhalation. The second set of valves is at the exhalation ports. The one-way valves placed there prevent room air from entering the mask during inhalation. They also allow the patient's exhaled gases to exit the mask during exhalation.