Breathing Air
Compressed air used for human respiration must meet strict purity standards that go beyond normal industrial requirements.
Applications
Breathing Air Uses
┌─────────────────────────────────────────────────────────┐
│ BREATHING AIR APPLICATIONS │
│ │
│ INDUSTRIAL │
│ ├─ Self-contained breathing apparatus (SCBA) │
│ ├─ Supplied air for painting │
│ ├─ Confined spaces │
│ ├─ Hazardous atmospheres │
│ └─ Asbestos/lead work │
│ │
│ MEDICAL │
│ ├─ Medical air │
│ ├─ Mechanical ventilators │
│ └─ Surgical procedures │
│ │
│ RECREATIONAL │
│ ├─ SCUBA diving │
│ ├─ Paintball │
│ └─ High altitude sports │
│ │
└─────────────────────────────────────────────────────────┘
Quality Standards
Standard Comparison
| Contaminant | OSHA Grade D | CGA G-7.1 Grade E | ISO 8573-1 |
|---|---|---|---|
| Oxygen | 19.5-23.5% | 20-22% | 20-22% |
| CO | < 10 ppm | < 10 ppm | < 5 ppm |
| CO₂ | < 1,000 ppm | < 500 ppm | < 500 ppm |
| Oil | < 5 mg/m³ | < 1 mg/m³ | < 0.5 mg/m³ |
| Dew point | - | -50°F PDP | -40°F PDP |
| Odor | None | None | None |
OSHA 29 CFR 1910.134
Minimum requirements for breathing air:
┌─────────────────────────────────────────────────────────┐
│ OSHA GRADE D │
├─────────────────────────────────────────────────────────┤
│ │
│ Oxygen: 19.5% - 23.5% │
│ │
│ Carbon monoxide (CO): ≤ 10 ppm │
│ │
│ Carbon dioxide (CO₂): ≤ 1,000 ppm │
│ │
│ Condensed hydrocarbons: ≤ 5 mg/m³ │
│ (as oil) │
│ │
│ Odor: None detectable │
│ │
│ If pressure >125 psig: │
│ • Dew point ≤ 10°F below ambient │
│ │
└─────────────────────────────────────────────────────────┘
Breathing Air System
System Architecture
Special Wet Specialized Continuous Use
compressor tank treatment monitor
│ │ │ │ │
▼ ▼ ▼ ▼ ▼
┌─────┐ ┌─────┐ ┌───────────┐ ┌─────┐ ┌─────┐
│ │ │ │ │Pre-filter │ │ │ │ SAR │
│ C │══►│ T │══►│Dryer │══►│ M │══►│SCBA │
│ │ │ │ │Carbon │ │ │ │ │
│ │ │ │ │Post-filter│ │ │ │ │
└─────┘ └─────┘ │Catalyst │ └─────┘ └─────┘
└───────────┘
C = Oil-free or special lubricated compressor
T = Receiver tank
M = CO and other monitors
Specialized Components
| Component | Function | Requirement |
|---|---|---|
| Compressor | Produce base air | Oil-free preferred |
| Pre-filter | Remove particles | 1 μm |
| Dryer | Reduce humidity | -40°F PDP |
| Carbon tower | Remove oil and odors | Regular replacement |
| Catalytic converter | CO → CO₂ | If CO risk exists |
| Post-filter | Carbon dust | 0.01 μm |
| CO monitor | Real-time alarm | Required |
Air Intake Location
Considerations for location:
✗ AVOID ✓ PREFERRED
Near: Near:
• Vehicle traffic • Clean air
• Engine exhaust • Elevated (>10 ft)
• Process vents • Upwind of
• Stored chemicals contaminants
• Paint areas • Away from discharges
┌─────────────────────────────────────────┐
│ │
│ Prevailing │
│ winds ════► │
│ ┌───┐ │
│ │Air│ ◄── Minimum │
│ [Contaminants] │intake│ height │
│ ↓ └───┘ 10 ft │
│ ═══════════════════════════════════ │
│ Plant │
└─────────────────────────────────────────┘
Monitoring
CO Monitor
Continuous monitoring system:
┌───────────────────────────────────────────┐
│ CO MONITOR │
│ │
│ ┌─────────────────────────────┐ │
│ │ [ 0 ] ppm │ │
│ │ │ │
│ │ ● Green: Normal (0-5 ppm) │ │
│ │ ● Yellow: Alert (5-10) │ │
│ │ ● Red: Danger (>10) │ │
│ │ │ │
│ │ [Audible alarm if >10 ppm] │ │
│ └─────────────────────────────┘ │
│ │
│ Last calibration: __/__/____ │
│ Next calibration: __/__/____ │
└───────────────────────────────────────────┘
Sampling Program
| Parameter | Frequency | Method |
|---|---|---|
| CO | Continuous + quarterly | Electrochemical sensor |
| CO₂ | Quarterly | Colorimetric tube |
| Oxygen | Quarterly | Paramagnetic sensor |
| Dew point | Quarterly | Hygrometer |
| Oil | Quarterly | Gravimetric |
| Particles | Quarterly | Counter |
Test Record
BREATHING AIR QUALITY RECORD
Date: __________ Time: __________ Technician: __________
Sample point: _________________________________
Parameter Result Limit Status
─────────────────────────────────────────────────────
Oxygen (%) _______ 19.5-23.5 [ ] OK [ ] Fail
CO (ppm) _______ ≤ 10 [ ] OK [ ] Fail
CO₂ (ppm) _______ ≤ 1,000 [ ] OK [ ] Fail
Oil (mg/m³) _______ ≤ 5 [ ] OK [ ] Fail
Dew point (°F) _______ ≤ ___ [ ] OK [ ] Fail
Odor _______ None [ ] OK [ ] Fail
Observations: _________________________________________
Corrective action (if applicable): _____________________
Signature: __________________
Maintenance
Service Frequencies
| Component | Frequency | Action |
|---|---|---|
| Pre-filter | Weekly | Check ΔP, change if >5 psi |
| Activated carbon | 3-6 months | Change per hours or tests |
| Catalyst | Annual | Verify efficiency |
| Post-filter | Monthly | Change per ΔP |
| CO sensor | 6 months | Calibrate |
| Complete system | Annual | Certification |
Activated Carbon Replacement
Factors that reduce carbon life:
High humidity ──► 50% reduction
High temperature ──► 30% reduction
High contaminants ──► Variable reduction
Excessive flow ──► Reduced efficiency
Replacement indicators:
• Service hours reached
• Positive oil/odor test
• Increased ΔP
• Color change (if visible)
Breathing Air Compressors
Recommended Types
| Type | Advantages | Disadvantages |
|---|---|---|
| Oil-free screw | No oil contamination | High cost |
| Oil-free piston | Economical, simple | Frequent maintenance |
| Lubricated + treatment | Flexible, economical | Critical treatment |
| Diaphragm | Ultra clean | Low capacity |
Specifications
Dedicated breathing air compressor:
┌─────────────────────────────────────────────────────────┐
│ │
│ COMPRESSOR REQUIREMENTS │
│ │
│ • Air intake in clean location │
│ • High-efficiency inlet filter │
│ • If lubricated: food-grade oil │
│ • Aftercooler with separator │
│ • Automatic drains │
│ • Labeled "BREATHING AIR" │
│ • NOT connected to industrial system │
│ │
└─────────────────────────────────────────────────────────┘
SCBA Cylinders
Safe Filling
| Verification | Requirement |
|---|---|
| Hydrostatic date | Current (every 5 years) |
| External condition | No visible damage |
| Valve | Operates correctly |
| Air quality | Certified |
| Maximum pressure | Do not exceed |
| Temperature | Limit increase |
Filling Process
1. Verify cylinder certification
│
▼
2. Inspect external condition
│
▼
3. Verify valve operation
│
▼
4. Connect to fill panel
│
▼
5. Fill SLOWLY (avoid heating)
│
▼
6. Verify final pressure
│
▼
7. Document fill
Documentation and Certification
Required Records
| Document | Retention |
|---|---|
| Quality tests | 3 years minimum |
| System maintenance | Life of equipment |
| Monitor calibration | 3 years |
| Annual certification | 3 years |
| Personnel training | Current + 3 years |
Life Safety
Poor quality breathing air can cause death. There is no margin for error. Follow all procedures and never skip tests or maintenance.