| To release oil and water buildup | |
| To check for leaks | |
| To verify they meet pressure requirements | |
| So they can be inspected |
| Immediately fail | |
| Cannot be used | |
| Can still be used several times | |
| Can be used indefinitely |
| Trailer brakes | |
| Emergency and parking brakes | |
| Cab brakes | |
| Air brakes |