The threshold limit value (TLV) for chlorine is 0.5 parts per million (ppm) averaged over an 8-hour workshift.

 The threshold limit value (TLV) for chlorine is 0.5 parts per million (ppm) averaged over an 8-hour workshift. The short-term exposure limit (STEL) for chlorine is 1 ppm. 

Here are some other exposure limits for chlorine:

NIOSH REL: The recommended airborne exposure limit is 0.5 ppm for a 15-minute work period. 

OSHA PEL: The ceiling is 1 ppm. 

NIOSH IDLH: The immediate dangerous to life or health level is 10 ppm. 

Chlorine is a greenish-yellow gas with a pungent, irritating odor. The odor threshold for chlorine is about 0.3 ppm, so if you can smell chlorine, you are likely near the level of concern. 

If you inhale chlorine, you should try to get fresh air or artificial respiration. You should also check your respiratory rate and note any trauma. If you don't have a pulse, you should provide cardiopulmonary resuscitation (CPR). If you are breathing laboredly, you should administer oxygen or respiratory support.