Regulatory Compliance
What is Threshold Planning Quantity Under India's MSIHC Rules?
Vinit Pandey · Published 4 August 2026
In short: Threshold Planning Quantity (TPQ) is the quantity of a hazardous chemical above which a facility becomes subject to Major Accident Hazard notification and associated statutory obligations under regulations such as India's MSIHC Rules, 1989.
Key takeaways
- Storage or handling above a chemical's specified TPQ triggers Major Accident Hazard (MAH) classification
- MAH obligations include a safety report, on-site emergency plan, and ERDMP support for the off-site plan
- Facilities with several chemicals below individual thresholds may still need aggregate hazard review
- MAH status should be reassessed whenever hazardous inventory changes materially, not only at commissioning
MSIHC Rules specify threshold quantities for listed hazardous chemicals; a facility storing or handling a listed chemical above its specified threshold becomes classified as a Major Accident Hazard (MAH) unit, triggering a distinct set of statutory obligations beyond general factory safety requirements.
MAH obligations commonly include preparation of a safety report, an on-site emergency plan, and support for the district authority's off-site emergency plan — collectively forming the basis of the facility's ERDMP.
Because TPQ is assessed per chemical and per site, a facility handling several hazardous chemicals, each individually below its own threshold, may still need to assess aggregate or combined hazard potential depending on the applicable regulatory interpretation and site-specific hazard review.
Inventory changes — increased storage capacity, a new hazardous raw material, or a process change altering intermediate quantities — can shift a facility's TPQ status, meaning MAH classification should be reassessed whenever hazardous inventory changes materially, not only at initial commissioning.