Tetrahydrofuran (109-99-9)
Tetrahydrofuran is a volatile organic compound with CAS Registry Number 109-99-9. 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 200 ppm. The principal target organs are the CNS; liver; skin, and workplace air is sampled and analyzed by NIOSH 1609.
Exposure Limits at a Glance
| Limit | Value | Basis |
|---|---|---|
| OSHA PEL (8-hr TWA) | 200 ppm | 29 CFR 1910.1000 |
| NIOSH REL | See note below | NIOSH Pocket Guide |
| Hazard Class | Volatile Organic Compound | VOC |
| Target Organs | CNS; liver; skin | NIOSH / OSHA |
| Sampling Method | NIOSH 1609 | 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 Tetrahydrofuran is assessed against the CNS; liver; skin — the organ systems most consistently affected in occupational studies. Employers must ensure no employee’s 8-hour TWA exceeds the 200 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 1609 for laboratory analysis.
- Medical surveillance: consult the OSHA substance-specific standards and the NIOSH Pocket Guide when the target organs are the CNS; liver; 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 1609 specifies media, flow, and analysis.
- Compare analytical results to the OSHA PEL of 200 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 Tetrahydrofuran?
The OSHA Permissible Exposure Limit (8-hour TWA) for Tetrahydrofuran is 200 ppm.
What is the CAS number for Tetrahydrofuran?
The CAS Registry Number for Tetrahydrofuran is 109-99-9.
What are the target organs for Tetrahydrofuran?
The primary target organs are the CNS; liver; skin.
How do you measure Tetrahydrofuran in workplace air?
Use NIOSH analytical method NIOSH 1609 for air sampling and laboratory analysis.
What hazard class is Tetrahydrofuran?
It is classified here as a Volatile Organic Compound (VOC).