ASHRAE 34 Safety Classifications
Complete guide to refrigerant toxicity and flammability ratings
Safety Classification Matrix
| Flammability → | ||||
|---|---|---|---|---|
| Toxicity ↓ |
Class 1
No Flame
|
Class 2L
Lower Flammability
|
Class 2
Flammable
|
Class 3
Higher Flammability
|
|
Class A
Lower Toxicity
|
A1 | A2L | A2 | A3 |
|
Class B
Higher Toxicity
|
B1 | B2L | B2 | B3 |
Classification Details
Class A1
Toxicity: Low | Flammability: None
Non-toxic, non-flammable. Safest classification for occupied spaces.
Safety Requirements
- No special ventilation requirements
- Standard tools and equipment
- No flame-proof equipment needed
- Suitable for all building types
Common Refrigerants
Class A2L
Toxicity: Low | Flammability: Mild (Lower Burning Velocity)
Non-toxic, mildly flammable with low burning velocity (<10 cm/s). Requires special handling.
Safety Requirements
- Leak detection required in equipment room
- Charge limits may apply (varies by application)
- No ignition sources near service ports
- A2L-rated recovery equipment recommended
- Ventilation during service operations
Common Refrigerants
Class A2
Toxicity: Low | Flammability: Flammable
Non-toxic but flammable. Higher burning velocity than A2L. Requires strict safety measures.
Safety Requirements
- Dedicated equipment room required
- Strict charge limits apply
- Flame-proof electrical equipment
- Emergency ventilation system
- Continuous leak monitoring
Common Refrigerants
Class A3
Toxicity: Low | Flammability: Highly Flammable
Non-toxic but HIGHLY FLAMMABLE. Hydrocarbon refrigerants. Explosion risk if ignited.
Safety Requirements
- Maximum charge limits: 150g (sealed) or per IEC 60335-2-89
- EXPLOSION-PROOF tools and equipment REQUIRED
- No open flames, sparks, or hot surfaces
- Work only in well-ventilated areas
- Gas is heavier than air - ventilate at floor level
- Specialized hydrocarbon leak detectors required
- Proper grounding to prevent static discharge
Common Refrigerants
Class B1
Toxicity: High | Flammability: None
Toxic but non-flammable. Requires respiratory protection and monitoring.
Safety Requirements
- Dedicated machinery room required
- Continuous ammonia/refrigerant monitoring
- Self-contained breathing apparatus (SCBA) available
- Emergency ventilation system
- Trained personnel only
- First aid equipment on-site
Common Refrigerants
Class B2L
Toxicity: High | Flammability: Mild (Lower Burning Velocity)
Toxic AND mildly flammable. Double hazard requires comprehensive safety measures.
Safety Requirements
- All B1 requirements plus:
- A2L flammability precautions
- Enhanced leak detection
- Emergency response plan required
Common Refrigerants
Class B2
Toxicity: High | Flammability: Flammable
Toxic AND flammable. Serious hazard requiring maximum safety precautions.
Safety Requirements
- Dedicated machinery room with explosion-proof equipment
- Continuous monitoring for both toxicity and flammability
- Full respiratory protection required
- Emergency ventilation and alarm systems
- Strict access control
Common Refrigerants
Class B3
Toxicity: High | Flammability: Highly Flammable
Toxic AND highly flammable. Maximum hazard classification. Rarely used in HVAC.
Safety Requirements
- Industrial applications only
- Full hazmat protocols required
- Not permitted in occupied buildings
- Specialized training mandatory
Common Refrigerants
Refrigerant Quick Reference
| Refrigerant | Class | GWP | Type | Notes |
|---|---|---|---|---|
| R-22 | A1 | 1810 | HCFC | Phased out (ODP) |
| R-32 | A2L | 675 | HFC | Common in Asia |
| R-134a | A1 | 1430 | HFC | Automotive/chillers |
| R-290 | A3 | 3 | HC | Natural refrigerant |
| R-404A | A1 | 3922 | HFC | Commercial ref. |
| R-407C | A1 | 1774 | HFC | R-22 replacement |
| R-410A | A1 | 2088 | HFC | Being phased out |
| R-449A | A1 | 1397 | HFC | R-404A replacement |
| R-454B | A2L | 466 | HFO | R-410A replacement |
| R-507A | A1 | 3985 | HFC | Commercial ref. |
| R-513A | A1 | 631 | HFO | R-134a replacement |
| R-600a | A3 | 3 | HC | Domestic fridges |
| R-717 | B1 | 0 | Natural | Ammonia |
| R-744 | A1 | 1 | Natural | CO2 |
| R-1234yf | A2L | 4 | HFO | Automotive |
| R-1234ze | A2L | 6 | HFO | Chillers |
A2L Refrigerants: What Technicians Need to Know
A2L refrigerants (like R-32, R-454B, R-1234yf) are becoming standard replacements for R-410A. Understanding their properties is critical for safe handling.
Key Characteristics
- Low Burning Velocity: <10 cm/s (Class 2 is >10 cm/s)
- LFL (Lower Flammability Limit): Typically 6-15% by volume
- Heat of Combustion: Low compared to Class 3
- Flame Propagation: Difficult to ignite, slow spread
Service Best Practices
- No brazing with refrigerant in system
- Recover to <0 psig before opening system
- Use electronic leak detectors rated for A2L
- Ensure adequate ventilation during service
- Keep ignition sources away from service ports
⚠️ A3 Hydrocarbon Refrigerants - CRITICAL SAFETY
R-290 (Propane), R-600a (Isobutane), and R-1270 (Propylene) are HIGHLY FLAMMABLE with explosion risk. Failure to follow safety procedures can result in fire, explosion, injury, or death.
Charge Limits
- • Sealed systems: Max 150g
- • Per IEC 60335-2-89
- • Domestic fridges: 50-100g typical
Required Equipment
- • Explosion-proof recovery unit
- • HC-rated leak detector
- • Anti-static grounding strap
NEVER Do
- • Use open flames nearby
- • Work in enclosed spaces
- • Use non-rated equipment
Flammability Data: R-290: LFL 2.1%, UFL 9.5% | R-600a: LFL 1.8%, UFL 8.4% | Flash point: -104°C (R-290)
Reference Standards
ASHRAE Standard 34 (Designation and Safety Classification of Refrigerants)
ISO 817 (Refrigerants — Designation and safety classification)
IEC 60335-2-89 (Safety of household electrical appliances)