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Engineering ToolBox > Ammonia - NH3 - Concentration in Air and Health Symptoms
Ammonia - NH3 - is a gas commonly used as a refrigerant in cooling systems. The gas is colorless with very sharp odor. In small concentrations the gas is detectable by smell. In high concentrations the gas is an immediate hazard to life.
| Ammonia concentration in air (ppm) | Health Symptoms |
| < 25 | Detectable by smell. Maximum Permissible Exposure Limit (PEL)1) |
| 30 | Uncomfortable, breathing support required. Maximum exposure 15 minutes1) |
| 50 | OSHA2) maximum exposure limit |
| 100 | Irritated eyes, throat and mucous membranes. Mild eye, nose, and throat irritation, may develop tolerance in 1-2 weeks with no adverse effects. |
| 140 | Moderate eye irritation, no long-term effect in exposures of less than 2 hours |
| 400 | Moderate throat irritation. Damage of mucous membranes with more than one hour exposure |
| 500 | Immediate danger to life limit (IDLH) |
| 1,000 | Caustic to airway |
| 1,700 | Fatal after short exposures - less than half an hour |
| 5,000 | Immediate hazard to life |
| > 15,000 | Full body protection required |
| 160,000 - 170,000 | Flammable in air at 50oC |
Lower Flammable Limit (LFL) of Ammonia in air is 15-16% by volume.