Worker safety is of utmost importance. Occupational health and safety professionals, called industrial hygienists, use chemical sampling and analysis to assess workplace chemical concentrations and the potential for worker exposures. The validity of an assessment is based in part on the procedures used for sample collection and analysis, and on data interpretation. In many instances, industrial hygienists use approaches that have been refined over many years and are accepted by professionals as good practice. However, the multitude of variables within a specific workplace requires the professional to exercise judgment in the design of a particular assessment.
Industrial Hygiene and Workplace Monitoring
Worker Safety and Occupational Exposure Levels
Occupational Exposure Limits (OELs) are intended to set the airborne concentrations of substances to which workers can be exposed on a daily basis without significant risk of adverse effects from the material. OELs are normally set for an eight hour day and are expressed as an eight hour time-weighted average. In many cases, a short-term (15-minute) exposure limit or Ceiling (C) value is also established.
The primary regulatory and professional organizations that establish OELs for airborne aliphatic diisocyanates include:
- American Conference of Governmental and Industrial Hygienists (ACGIH) Threshold Limit Value (TLV)
- National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL)
Note: The Occupational Safety and Health Administration (OSHA) has not established Permissible Exposure Limits (PELs) for aliphatic diisocyanates.
| Isocyanate | ACGIH-TLV (ppm) | NIOSH-REL (ppm) |
|---|---|---|
| HDMI | 0.005 (8-hr TWA) | 0.010 (C) |
| 1,6-HDI | 0.005 (8-hr TWA) | 0.005 (8-hr TWA) 0.020 (STEL) |
| IPDI | 0.005 (8-hr TWA) | 0.005 (8-hr TWA) 0.020 (STEL) |
C = Ceiling Limit (concentration that should not be exceeded during any part of the work shift)
TWA = Time Weighted Average (average airborne concentration over an 8-hour work shift)
STEL = Short Term Exposure Limit (15-minute average airborne concentration that should not be exceeded at any time during the work shift)
PPM = parts per million (0.020 ppm is equivalent to 20 parts per billion or 20 ppb; 0.005 ppm is equivalent to 5 ppb)
Current regulations should always be consulted for compliance purposes. To learn more about ADI concentration limits, consult with NIOSH, OSHA, or ACGIH, and the product manufacturer. To protect workers, the ADI industry uses many tools to monitor worker exposure as outlined below.
Industrial Hygiene & Workplace Monitoring Resources
OSHA Sampling & Analytical Methods
- OSHA Analytical Methods - An index of sampling and analytical methods for chemicals that have either a validated or partially validated OSHA method
The following methods have been withdrawn by OSHA (for historical reference only):
- Diisocyanates Organic Method #42 (includes HDI)
- Partially Validates Method PV2030 (HDI Biuret)
- Partially Validated Method PV2034 (IPDI)
- Partially Validated Method PV2092 (HMDI)
- Partially Validated Method PV2125 (HDI Homopolymer)
Wipe Method
- 1,6-Hexamethylene Diisocyanate: Method # W4002
- OSHA Technical Manual (OTM) Section II: Chapter 2 (Wipe Sampling Methodology)
Note: Commercially available “isocyanate wipe testing” products are available for this sampling methodology. Additional information when considering Wipe Sampling is available here.
Additional sampling methods and information about diisocyanates can be found on OSHA’s website.
ASTM Standards
The American Society for Testing and Materials (ASTM) has developed several standards for testing of ADI. The following links are to summaries of test standards; the ASTM website provides information on how to order the full documents:
- ASTM D6562 - 20 Standard Test Method for Determination of Gaseous Hexamethylene Diisocyanate (HDI) in Air with 9-(N-methylaminomethyl) Anthracene Method (MAMA) in the Workplace
- ASTM D6561 - 20 Standard Test Method for Determination of Aerosol Monomeric and Oligomeric Hexamethylene Diisocyanate (HDI) in Air with (Methoxy-2–phenyl-1) Piperazine (MOPIP) in the Workplace
- ASTM D2572 - 19 Standard Test Method for Isocyanate Groups in Urethane Materials or Prepolymers
NIOSH Manual of Analytical Methods
NIOSH has developed a manual of analytical methods that it has evaluated. Chapter K of the manual discusses issues concerning sampling and analysis of airborne aliphatic diisocyanates. In addition, the manual provides the following analytical methods:
- Isocyanates (includes HDI - Method 5522)
- Isocyanates, Monomeric (includes HDI - Method 5521)
- Isocyanates, Total MAP (includes HDI - Method 5525)
International Organization for Standardization (ISO): (for purchase)
- Workplace air - Guidelines for selecting analytical methods for sampling and analyzing isocyanates in air
Summary: ISO/TR 17737:2012 provides guidelines which are intended to provide industrial hygienists, employers and workers with a broad overview of isocyanates, their uses in industry, methods of measurement and guidance on choosing the appropriate sampling strategy.
Related Topics
In addition to industrial hygiene testing and reporting methodologies designed to protect worker health, there is a variety of environmental monitoring and airborne emissions testing and reporting methodologies and requirements. Visit the Environmental Emissions Reporting and Testing section of this website for information and resources on environmental airborne emissions reporting and testing.