The amount of breathing air consumed during a monthly SCBA functional test (often referred to as the “monthly inspection” or “flow test”) varies slightly by manufacturer and the specific depth of your inspection/testing SOP. However, for a standard 30-minute/45-cubic-foot cylinder, you can estimate the usage based on the required NFPA 1852 checks.
On average, a standard monthly functional check consumes between 350 psig and 600 psig (approximately 7 to 12 cubic feet) of air.
Here is the breakdown of where that air goes during the test:
- System Pressurization & Leak Check: High-pressure leak tests require the system to be fully pressurized. Opening the cylinder valve fills the high-pressure hose and the regulator’s internal plumbing. Closing it and watching for a pressure drop (usually less than 100 psi over 1 minute) consumes a negligible amount of air, but the initial “fill” stays in the lines.
- Low-Pressure Alarm (Vibr-Alert/Bell): To test the alarm, you must bleed the air slowly from the system. The alarm usually activates when the pressure drops to approximately 25% to 33% of the service pressure (roughly 550–700 psig for a 2216 system). This air is effectively “dumped” to the atmosphere.
- Regulator/Facepiece Check: Taking 2–3 deep breaths to verify that the regulator is delivering air and that the exhalation valve is functioning.
- An average adult breath is roughly 0.05 to 0.1 cubic feet (1.5 to 3 liters).
- Testing the bypass/purge valve for 1–2 seconds can dump 2 to 3 cubic feet of air very quickly.
If you are performing this check once a month per pack:
| Component | Air Consumed (psig) | Air Consumed (ft³) |
| Leak/Static Test | ~50 psig | ~1.0 ft³ |
| Bypass/Purge Check | ~150–200 psig | ~3.5 ft³ |
| Alarm Bleed-down | ~150–200 psig | ~3.5 ft³ |
| User Breaths | ~50 psig | ~1.0 ft³ |
| Total per SCBA | ~400–500 psig | ~9–10 ft³ |
Factors That Increase Usage
- HUD Verification: If your units have a Heads-Up Display, you may spend more time bleeding air slowly to ensure each light (Green, Yellow, Red) triggers at the correct pressure intervals.
- The “Purge” Habit: If the inspector leaves the bypass valve open longer than 2 seconds, consumption can easily double.
- Training Overlay: If the functional test is combined with a quick “donning and doffing” drill, air usage can jump to 1,000+ psig (half a bottle).
For a facility with 10 SCBAs, you should plan for at least two full 2216 psig cylinders (or one 4500 psig cylinder) per month just to cover the functional testing requirements and subsequent refilling of the packs to ensure they are at the “Full” mark for service.
Sources: Me, NFPA, Gemini+