10 ppm = 1/1000 of 1% Can smell. Safe for 8 hours exposure 100 ppm = 1/100 of 1% Kills smell in 3 to 15 minutes. May sting eyes and throat 200 ppm = 2/100 of 1% Kills smell shortly. Stings eyes and throat 500 ppm = 5/100 of 1% Loses sense of reasoning and balance. Respiratory paralysis in 30 to 45 minutes. Needs prompt artificial resuscitation. Will become unconscious quickly (15 minutes maximum) 700 ppm = 7/100 of 1% Breathing will stop and death will result if not rescued promptly. Immediate artificial resuscitation is required 1,000 ppm = 1/10 of 1% Immediate unconsciousness. Permanent brain damage may result unless rescued promptly.
