California BAAQMD Portable Engine Permit Reference

Why this matters

Any diesel-fueled engine over 50 brake horsepower (bhp) operating in the nine-county Bay Area Air Quality Management District (BAAQMD) jurisdiction needs either a BAAQMD Authority to Construct / Permit to Operate OR a CARB Portable Equipment Registration Program (PERP) registration. Job-site portable generators that the contractor moves between sites cannot use a stationary-source BAAQMD permit - they need PERP if the unit truly qualifies as portable. Get this wrong and you eat BAAQMD Regulation 2-1 violation notices, CARB civil penalties under Health and Safety Code 42402 (statutory maximum 10,000 per day per violation for negligent violations, 75,000 per day per violation for knowing violations), and the customer's site gets shut down. This reference covers the decision tree, registration mechanics, and the daily-log requirements that field crews actually have to comply with.

Stationary vs portable - the threshold test

CARB defines portable under 17 CCR 93116.2(a)(31) as equipment designed and capable of being carried or moved from one location to another, with the equipment NOT remaining at any single location for more than 12 consecutive months OR the time required to complete the relocatable activity, whichever is shorter. A "location" is the entire contiguous property owned, leased, or operated by the same entity.

If the generator sits at one job site for 12 months and one day, it becomes stationary as a matter of law and CARB PERP coverage lapses. At that point BAAQMD requires either an Authority to Construct (Reg 2-1-301) before installation or a Permit to Operate (Reg 2-1-302) after installation. Stationary diesel engines over 50 bhp at non-emergency-only service also must meet the CARB Airborne Toxic Control Measure (ATCM) for Stationary Compression Ignition Engines (17 CCR 93115).

Emergency-standby engines have a separate carve-out under 17 CCR 93115.4(a)(3) - up to 50 hr per year for testing and maintenance plus unlimited emergency use is allowed without Tier 4 final compliance, but ONLY if the engine is dedicated to emergency service at a fixed location with a BAAQMD permit.

Tier 4 final and ATCM emissions floor

PERP-registered engines manufactured 2024 model year and later must be EPA Tier 4 final-certified. Tier 4 final NOx + NMHC limits per 40 CFR 1039.101 for engines 56 to 130 kW are 0.40 g/kWh NOx + NMHC and 0.025 g/kWh PM. Pre-2014 Tier 2 or Tier 3 engines can still hold PERP registration but only with documented installation of a Diesel Particulate Filter (DPF) verified under the CARB Verification Procedure (17 CCR 2700-2710).

BAAQMD Regulation 9 Rule 8 (Nitrogen Oxides and Carbon Monoxide from Stationary Internal Combustion Engines) sets stricter local NOx limits than the EPA federal floor - for diesel engines 50 to 500 bhp installed after 1 January 2010, the NOx limit is 65 ppmvd at 15 percent O2 or 0.5 g/bhp-hr, whichever is more restrictive. Field crews installing replacement standby engines must verify the BAAQMD Reg 9-8 cap against the engine's certification data plate before commissioning.

PERP registration workflow

PERP applications are filed online through the CARB DOORS portal (https://ssl.arb.ca.gov/ssldoors). Required documents:

1. Engine certification executive order number (EO) from the CARB Off-Road Compression Ignition Engine list.
2. Manufacturer, model, model year, serial number, rated bhp.
3. Aftertreatment configuration (DPF or none) with verification level (Level 3 PM required for any pre-Tier 4 engine staged inside the BAAQMD).
4. Fuel type and sulfur certification (CARB diesel under 15 ppm S).
5. Owner contact and operator contact (often different - the owner is the rental house, the operator is the contractor at the site).

PERP issues a unique registration number formatted PE-YYYY-NNNNNN and a sticker that must remain affixed to the engine enclosure. Registration is valid statewide and is renewed every 3 years per 17 CCR 2455.

Daily on-site recordkeeping

PERP-registered engines must keep an hour-meter log on the engine and a written daily log accessible at the site. The log must capture per 17 CCR 2456(b):

• Date of operation
• Site address and APN if available
• Start hour-meter reading and end reading
• Total run hours that day
• Fuel consumed (gallons) - reasonable estimate accepted, do not need a flow meter
• Operator name and signature

Inspectors from BAAQMD or CARB will ask for the past 24 months of logs on demand. Missing logs are an automatic violation regardless of whether the engine was operating legally.

Stationary permit path - when PERP will not work

If the engine will live at a single site over 12 months, file BAAQMD Form for Authority to Construct under Reg 2-1-301 BEFORE installation. Required information:

• Site address and APN
• Engine make, model, bhp, EPA tier, Executive Order number
• Hours of operation per year (max 200 hr for non-emergency, unlimited for true emergency standby)
• Stack height and orientation
• Distance to nearest sensitive receptor (school, hospital, residence) - drives the Health Risk Assessment requirement

Health Risk Assessment under BAAQMD Reg 2-5 is triggered if cancer risk exceeds 10 in a million or chronic hazard index exceeds 1.0. Most stationary standby diesel installs under 500 kW at industrial sites pass without HRA; residential-adjacent installs frequently do not.

Application fees vary by engine size and apply per CARB and BAAQMD published fee schedules - confirm the current schedule on the BAAQMD Permit Services page before quoting permitting to the customer.

Common field mistakes

Treating a generator as portable when it has been at one customer site over a year. PERP coverage silently lapses and the operator becomes the responsible party.

Forgetting that BAAQMD Reg 9-8 is stricter than EPA Tier 4 federal floor on NOx. A federally-certified Tier 4 final engine can still violate the local NOx limit if the manufacturer set the calibration to the federal floor.

Running an emergency-standby engine over the 50 hr/year non-emergency cap. The hour meter is the proof - if the cap is exceeded the engine loses its ATCM exemption and must meet stationary non-emergency standards retroactively, which usually means a DPF retrofit.

Not posting the PERP sticker visibly on the engine enclosure. Inspectors cite this even when the registration is valid in DOORS.

References

• California Code of Regulations Title 17 Section 93115 (ATCM for Stationary Compression Ignition Engines)
• California Code of Regulations Title 17 Section 93116 (Portable Engine ATCM)
• California Code of Regulations Title 17 Sections 2450-2465 (Portable Equipment Registration Program)
• BAAQMD Regulation 2 Rule 1 (Permit Requirements)
• BAAQMD Regulation 9 Rule 8 (NOx and CO from Stationary Internal Combustion Engines)
• 40 CFR Part 1039 (Control of Emissions from New and In-Use Nonroad Compression-Ignition Engines)
• California Health and Safety Code Section 42402 (Civil Penalty Schedule)