Smoke School Information in California

California Acceptance Status for VirtualOpacity^® — EPA ALT-152A

Accepted.

California Visible Emissions / Opacity Standard

The opacity limit for California is Statewide statute: Ringelmann No. 2 / 40% opacity equivalent; most districts impose 20% (Ringelmann 1) via district rules, as established under Cal. Health & Safety Code Sec. 41701(a)-(b) (statewide statute); exemptions Sec. 41704; district rules stricter (e.g., SCAQMD Rule 401: Ringelmann 1 / 20%).

Compliance is demonstrated via EPA Method 9 or California ARB Method.

Averaging period: Statute: periods aggregating more than 3 minutes in any one hour; district rules vary (SCAQMD Rule 401 uses 3-min aggregate)

statewide floor is HSC § 41701 — Ringelmann 2 (40% equivalent) for >3 min aggregate/hr. The 20%/Ringelmann 1 figure describes district rules (e.g., SCAQMD Rule 401), not the state statute. Exemptions listed in HSC § 41704. Method 9 / district-certified observers used for enforcement.

Last verified July 8, 2026

Note: Regulations change — always verify current requirements with your state's air quality agency before making compliance decisions. This page is for informational purposes and is not legal advice; consult a qualified attorney or environmental compliance professional for guidance specific to your facility.