The “polymeric” form of MDI (p-MDI or PMDI) is typically 30 percent to 70 percent diphenylmethane diisocyanate
- The threshold limit value (TLV) for MDI is 0.005 ppm (parts per million) or 5 ppb (parts per billion), expressed as a TWA. This is a value from the ACGIH (American Conference of Governmental Industrial Hygienists) and is not a mandatory guideline.
- The OSHA permissible exposure limit (PEL) – a 20 ppb ceiling – is the standard for compliance in the United States.
- the National Institute for Occupational Safety and Health (NIOSH) and the ACGIH have recommended an 8-hour TWA for MDI of 0.005 ppm (equivalent to 0.051 mg/m3).