1 ppm = 1/10000 of 1%

Can be smelled
 

10 ppm = 1/1000 of 1%

Occupational Exposure Limit (OEL). Allowable for 8 hours of exposure
 

15 ppm = 1/500 of 1%

Ceiling OEL. At this level of concentration workers must wear appropriate breathing apparatus.
 

100 ppm = 1/100 of 1%

Loss of smell in 2 to 15 minutes. May burn throat, cause headache and nausea.
 

200 ppm = 2/100 of 1%

Sense of smell lost rapidly. Burns eyes and throat.
 

500 ppm = 5/100 of 1%

Loss of reasoning and balance. Respiratory disturbances in 2 to 15 minutes. Prompt resuscitation needed.
 

700 ppm = 7/100 of 1%

Immediate unconsciousness. Causes seizures, loss of control of bowel and bladder. Breathing will stop and death will result if not rescued promptly. Immediate resuscitation needed.
 

1000 ppm = 1/10 of 1%

Causes immediate unconsciousness. Death or permanent brain damage may result unless rescued promptly.