Propylene Oxide (75-56-9)
Propylene Oxide is a volatile organic compound with CAS Registry Number 75-56-9. Under the OSHA air contaminants standard (29 CFR 1910.1000), its Permissible Exposure Limit (PEL) — the legal 8-hour time-weighted average (TWA) for general industry — is 100 ppm. The principal target organs are the Respiratory tract; eyes; skin, and workplace air is sampled and analyzed by NIOSH 1612.
Exposure Limits at a Glance
| Limit | Value | Basis |
|---|---|---|
| OSHA PEL (8-hr TWA) | 100 ppm | 29 CFR 1910.1000 |
| NIOSH REL | See note below | NIOSH Pocket Guide |
| Hazard Class | Volatile Organic Compound | VOC |
| Target Organs | Respiratory tract; eyes; skin | NIOSH / OSHA |
| Sampling Method | NIOSH 1612 | NIOSH Manual of Analytical Methods |
NIOSH REL note: TWA values in the ppm range; NIOSH RELs are frequently 10x stricter than the OSHA PEL. The REL is a non-regulatory recommendation; where a NIOSH REL exists it is typically more protective than the OSHA PEL.
How It Enters the Body & Health Effects
Exposure to Propylene Oxide is assessed against the Respiratory tract; eyes; skin — the organ systems most consistently affected in occupational studies. Employers must ensure no employee’s 8-hour TWA exceeds the 100 ppm PEL, and must use engineering controls, work practices, and — where required — respiratory protection to keep exposures at or below that level.
- Hazard class: Volatile Organic Compound. VOC-class agents are managed with the hierarchy of controls (elimination, substitution, engineering controls, administrative controls, then PPE).
- Monitoring: collect personal air samples in the breathing zone and submit them under NIOSH 1612 for laboratory analysis.
- Medical surveillance: consult the OSHA substance-specific standards and the NIOSH Pocket Guide when the target organs are the Respiratory tract; eyes; skin.
Sampling & Compliance Notes
- Determine whether the exposure is a full-period 8-hour TWA or a short-term / ceiling scenario. Ceiling and STEL excursions apply to several VOC-class agents regardless of the 8-hour average.
- Calibrate personal sampling pumps before and after each shift and record flow rates; method NIOSH 1612 specifies media, flow, and analysis.
- Compare analytical results to the OSHA PEL of 100 ppm and the NIOSH REL. Document the higher of the two for internal exposure-control targets.
- Where the PEL includes a “skin” notation, dermal absorption can contribute to the dose — glove selection and hygiene facilities are part of compliance.
Frequently Asked Questions
What is the OSHA PEL for Propylene Oxide?
The OSHA Permissible Exposure Limit (8-hour TWA) for Propylene Oxide is 100 ppm.
What is the CAS number for Propylene Oxide?
The CAS Registry Number for Propylene Oxide is 75-56-9.
What are the target organs for Propylene Oxide?
The primary target organs are the Respiratory tract; eyes; skin.
How do you measure Propylene Oxide in workplace air?
Use NIOSH analytical method NIOSH 1612 for air sampling and laboratory analysis.
What hazard class is Propylene Oxide?
It is classified here as a Volatile Organic Compound (VOC).