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NESHAP Subpart GG aerospace 3-stage chromate filtration

If your shop applies chromated primers or topcoats covered under the aerospace coatings rule, Boeing, Lockheed, defense supplier work, you're under NESHAP Subpart GG. The rule is more rigorous than collision-shop area-source rules because chromium emissions are more hazardous and the aerospace coatings industry has specific federal recordkeeping expectations. The defining technical requirement is 3-stage filtration with a HEPA-class final stage; the defining documentation requirement is capture-test data per stage tracked through the maintenance log.

Quick answer

NESHAP Subpart GG covers aerospace manufacturing and rework facilities applying chromated primers and topcoats. The rule requires 3-stage filtration with HEPA-class final-stage media, full capture-test documentation, and maintenance logs that track per-shift filter inspection. Tier-1 and tier-2 aerospace suppliers fall under the same rule as the OEM facilities.

By Ben Kurtz · Filter Fitment Lead, 20+ years in paint-booth service · Updated May 9, 2026
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What this means for filter selection

Stage 1 is the primary intake-ceiling diffusion media (as in collision booths). Stage 2 adds an intermediate-efficiency capture stage (typically MERV 13-15 panel filter or equivalent). Stage 3 is the HEPA-class final stage, capturing 99.97% of particulate at 0.3 micron, including chromium-bearing particulate. The 3-stage stack ensures the chromium emissions don't reach the environment.

Capture-test data for each stage ships with the filter. The shop's maintenance log tracks installation date, the spec sheet, and (for higher-throughput facilities) periodic source-test data confirming in-use capture against the rated value. Subpart GG-rated kits in the catalog ship with the relevant capture documentation formatted for federal aerospace recordkeeping.

Cycle math for Subpart GG kits is engineering-driven, not catalog-default, the OEM customer's coating specification typically prescribes the cycle. Boeing supplier programs, Lockheed supplier programs, and the broader defense aerospace supplier base each carry their own customer-side requirements that layer on top of the federal rule.

HEPA-class final-stage media is significantly more expensive per cycle than collision-class media. The cost-per-cycle reflects the regulatory rigor; the alternative (operating outside Subpart GG when the rule applies) is not a legal alternative.

Regulatory landscape

Subpart GG inspections are typically more rigorous than area-source inspections. Capture-test data for the installed media, maintenance log demonstrating per-shift inspection, technician training records on the chromated-coating-handling protocols, and (for higher-throughput facilities) source-test data are all expected. Subscription delivery records covering the 3-stage stack documented per shipment cover the maintenance log piece by default.

NESHAP Subpart GG aerospace 3-stage chromate filtration FAQs

How do I know if my shop falls under Subpart GG?

If you apply chromated primers or topcoats specified for aerospace components, even if you're a small tier-2 supplier finishing a single bracket, you're under the rule. The chromium content of the coating triggers applicability regardless of throughput volume. Check with your OEM customer or your state DEQ if uncertain.

Can I use collision-class kits on a Subpart GG booth?

No. Collision-class media doesn't include the 3-stage stack with HEPA-class final stage. Operating a Subpart GG-applicable booth with collision-class media is a federal violation.

What's the cost difference vs collision-class?

Per cycle, Subpart GG kits typically run 3-5x the cost of collision-class kits due to the HEPA-class final-stage media and the additional capture documentation. Per shop, the cost is meaningfully higher; the OEM customer's pricing for chromated-coating work typically reflects the operating cost.

Do all aerospace coatings require Subpart GG?

No, non-chromated aerospace coatings may fall under different rules or under the more general Subpart GG provisions for non-chromated work. The chromated-coating-specific 3-stage requirement is the rigorous case. Check the rule text for your specific coating chemistry.

What does an EPA Subpart GG inspection look like?

Document review (capture-test data per installed media, maintenance log, technician training records, source-test data where required) plus visual inspection of the booth's filter installation and operating condition. The inspection cadence is more frequent than area-source inspections.

How do source tests interact with the filter cycle?

Source tests are periodic measurements of the actual emissions leaving the facility, compared to the rated capture of the installed filtration. A failed source test indicates the filtration isn't performing as rated, either the media has failed, or the operating conditions have shifted. Subscription delivery on the engineering-spec cadence is the prevention path.

Sources

Primary references cited on this page.

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