1. Remove the air filter.
2. Inspect the air filter.
Note

Air filter removal/installation
A/c unit removal/installationMazda 6 Service Manual: Air intake actuator inspection
1. Connect battery positive voltage to terminal D or F and ground to terminal
F or D of the air intake actuator.
2. Verify that the air intake actuator operates as shown below.
If not as specified, replace the air intake actuator.
...
Mazda 6 Service Manual: Curtain Air Bags
The curtain air bags are mounted in the front and rear window pillars, and the
roof edge along both sides.
When the air bag crash sensors detect a side impact of greater than moderate
force, the curtain air bag inflates quickly and helps to reduce injury mainly to
the rear outboard passenger' ...