Definition:
ERPG, or Emergency Response Planning Guidelines, are airborne concentration thresholds developed by the AIHA (American Industrial Hygiene Association) which supports emergency planning for short-term, one-time exposures to toxic chemicals. ERPG values are intended primarily for public protection and emergency response planning (typically based on up to 1 hour of exposure).
ERPGs are U.S.-centric, but they are widely referenced internationally and are often borrowed into process safety and risk analysis as consequence severity endpoints for toxic release scenarios.
Note: AEGL, ERPG, and IDLH are all acute inhalation benchmarks and are often shown side‑by‑side in dispersion and emergency‑planning tools, which can cause confusion. AEGL and ERPG are public‑exposure guidelines for one‑time release scenarios, whereas IDLH is a NIOSH worker‑protection value for respirator/entry decisions; they are not interchangeable and must be used only for their intended purpose.
Key Points:
- ERPGs are developed by the AIHA Guideline Foundation (Emergency Response Planning program).
- ERPGs address acute inhalation toxicity used in dispersion and consequence modeling. Chemicals that are only flammable (with little acute toxicity) may not have meaningful ERPG values.
- Three levels are defined (typically for up to 1 hour of exposure):
- ERPG-1: Mild, transient effects or objectionable odor
- ERPG-2: Serious or irreversible effects, or impaired ability to take protective action
- ERPG-3: Life-threatening effects
- ERPGs could be fed into functional safety decision making and H&RA.
Example:
For a toxic gas release scenario, a facility chooses to compare dispersion modeling results against ERPG thresholds to estimate impact distances for different health effect levels. For chlorine, the commonly referenced ERPG values (ppm, 1-hour basis) are:
- ERPG-1 = 1 ppm
- ERPG-2 = 3 ppm
- ERPG-3 = 20 ppm
In this case, the facility uses ERPG-2 to identify the distance where nearly all individuals could still take protective action, and ERPG-3 to identify areas of potentially life-threatening exposure.
See Also: OSHA, H&RA, dispersion analysis, IDLH, AEGL
Cited Source:
- AIHA® Guideline Foundation – ERPG overview and definitions: https://www.aiha.org/get-involved/aiha-guideline-foundation/erpgs
- AIHA ERPG table and level definitions: https://erpg.aiha.org/Content/ERPG.cfm
- NOAA – ERPGs overview (public exposure guidelines context): https://response.restoration.noaa.gov/oil-and-chemical-spills/chemical-spills/resources/emergency-response-planning-guidelines-erpgs.html
- OSHA Chemical Database (at times displays ERPG values): https://www.osha.gov/chemicaldata