Chlorine gas is primarily a respiratory irritant. At low concentrations, chlorine gas has an odor similar to household bleach. As the concentrations increase from the level of detection by smell, so do the symptoms in the exposed individual. Depending on the level of exposure to chlorine, the effects may become more severe for several days after the incident. Observations of exposed individuals should be considered part of the medical response program.
The following list is a compilation of potential chlorine exposure thresholds and potential responses in humans, with considerable variation among subjects:
Chlorine Exposure Thresholds, Limits, and Guidelines (ppm)
| 0.2 - 0.4 |
Odor threshold (decrease in odor perception occurs over time) |
| < 0.5 |
No known acute or chronic effect |
| 0.5 |
ACGIH TLV-TWA (8-hour time-weighted average) |
| 1 |
OSHA PEL (ceiling)
ACGIH TLV-STEL (15 minutes)
AIHA ERPG-1: The maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing other than mild transient adverse health effects or perceiving a clearly defined, objectionable odor. |
| 1 - 3 |
Mild mucous membrane irritation, tolerated up to 1 hour |
| 3 |
AIHA ERPG-2: The maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual’s ability to take protective action. |
| 5 - 15 |
Moderate irritation of the respiratory tract. The gas is very irritating, and it is unlikely that any person would remain in such an exposure for more than a very brief time unless the person is trapped or unconscious |
| 10 |
NIOSH IDLH: The airborne concentration that poses an immediate threat to life, would cause irreversible adverse health effects, or would impair an individual's ability to escape from a dangerous atmosphere. Values are based on a 30-minute exposure. |
| 20 |
AIHA ERPG-3: The maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing or developing life-threatening health effects. |
| 30 |
Immediate chest pain, vomiting, dyspnea (shortness of breath), and cough |
| 40 - 60 |
Toxic pneumonitis (inflammation of the lungs) and pulmonary edema (accumulation of fluid in the lungs) |
| 430 |
Lethal over 30 minutes |
| 1000 |
Fatal within minutes. |
