What “Cleaned to Bare Metal” Actually Means (And Why It Matters for Your Insurance)

Nearly every hood cleaning company in Toronto will tell you that NFPA 96 requires cleaning to bare metal. It doesn’t, and we said the same thing on this page until we went back and checked the standard itself. Here is what NFPA 96 actually requires, why we clean to bare metal anyway, and why the distinction matters when your insurer audits your records after a claim. It’s the standard we bring to every kitchen we clean, from Mississauga to Vaughan.

Here’s what it actually means, and why it matters.

The technical definition

Ontario adopts NFPA 96 directly. Fire Code O. Reg. 213/07, Articles 2.6.1.12 and 2.6.1.13, require commercial cooking exhaust systems to be provided and maintained in accordance with the standard, and Table 1.2.1.A designates the 2014 edition. So the governing text here is Chapter 11, not Chapter 12, which is the renumbered equivalent in editions Ontario has not adopted.

Section 11.6.2 sets the cleaning requirement: “Hoods, grease removal devices, fans, ducts, and other appurtenances shall be cleaned to remove combustible contaminants prior to surfaces becoming heavily contaminated with grease or oily sludge.” Combustible contaminants, not bare metal. The phrase “bare metal” has been out of NFPA 96 for roughly two decades. It is in neither the 2014 edition Ontario uses nor the current 2024 one.

So why do we still use the term? Because “remove the combustible contaminants” is a threshold, and bare metal is the only outcome you can actually verify. When you look at the inside of a cleaned hood, plenum or duct, you should see metal, not a film, not a thin coating, not “almost clean.” Metal. A photograph can prove that. It cannot prove a residual film measured in microns.

This standard applies to the entire exhaust path, not just the visible hood: the hood itself (interior and exterior surfaces), grease removal devices (filters and baffles), the plenum (the chamber above the filters where grease accumulates first), the duct run from the hood to the rooftop, the exhaust fan (housing, blades, and discharge), and rooftop grease containment systems.

Why removing all of it matters

Grease is the fuel source for nearly every kitchen exhaust fire. A small amount of residue, even what looks like a “thin film”, can ignite from a flare-up on the cookline below, run up the duct, and spread to the rooftop fan. From there, it can ignite the roof structure, adjacent ductwork, or anything within the discharge zone.

This is why we hold to bare metal rather than to the threshold. A duct with 90% of its grease removed still has enough fuel to sustain a fire. The code language sets a minimum condition; removing everything is what actually takes the fuel out of the system.

Where contractors cut corners

This is the part most restaurant owners don’t see. A hood cleaning service typically takes between 2 and 5 hours depending on system size and condition. Done correctly, it includes filter removal and soaking in a degreaser solution; hood interior scraped and pressure-washed; plenum opened (this requires removing access panels) and degreased; duct interior cleaned via access panels along the run (which means cutting and re-sealing access doors where they don’t exist); exhaust fan disassembled with fan blades, housing, and motor compartment all degreased; rooftop grease containment cleaned and the area below the fan inspected; and photo documentation of every cleaned component.

Compare that to a “fast” hood cleaning, typically 60 to 90 minutes total. The math doesn’t work. To finish in 90 minutes, the contractor is skipping the plenum, skipping the duct interior, or skipping the fan. Whatever’s hidden behind an access panel, they’re not touching. The visible parts look clean. The hidden parts don’t.

If you’ve been getting hood cleaning that finishes in under two hours and you can’t recall a contractor actually disassembling the fan or accessing the duct interior, you’re almost certainly being charged for a partial clean.

Why your insurance specifically asks

Commercial insurance carriers in Ontario have gotten increasingly sophisticated about kitchen fire claims. When they investigate, they ask three things: Was the system cleaned at the NFPA 96-required frequency? Was it cleaned to bare metal? Can you provide before-and-after photo documentation of the entire system, including hidden components?

If the answer to any of those is “no,” you are in a much weaker position. Many commercial property policies carry a protective safeguards condition tied to your suppression and exhaust systems, a clause requiring you to keep them in working order, and where such a condition applies and is breached, the issue is not a higher premium at renewal but whether the policy responds to the loss at all. If the fire originated in the duct or fan, which is where most grease fires propagate to, and your documentation only shows the hood interior, you have a gap exactly where the investigation will look. Ask your broker whether your policy carries that condition and what it requires of your kitchen exhaust system.

The photo documentation requirement is the part most operators don’t realize. A piece of paper saying “system cleaned” isn’t enough. The insurer wants to see the duct interior, the plenum interior, the fan housing. If the contractor didn’t open those components, there are no photos. If there are no photos, there’s no proof of compliance.

What you should actually be getting from your contractor

A compliant hood cleaning service should hand you, within 24 hours of completing the job: a written service certificate documenting date, technician, scope of work, and NFPA 96 compliance; photos of the hood, plenum interior, duct interior at every access point, the exhaust fan disassembled and cleaned, and the rooftop grease containment, all before and after.

If you’re not getting all of that, you’re not getting NFPA 96 compliance, regardless of what the invoice says.

How to verify what you’re paying for

The easiest test: ask your current contractor for the most recent before-and-after photo set from your last cleaning. A compliant contractor will have them on file and can email them in minutes. A non-compliant contractor will hedge, delay, or tell you “we don’t usually do photos.” That answer is the test result.

We provide before-and-after photo documentation for every NFPA 96 component on every job (hood, plenum, ducts, fan, rooftop) within 24 hours of service. If you’re not currently getting this from your hood cleaner, we’ll come walk your system for free and show you what compliant documentation actually looks like.

Book Free On-Site Evaluation or call 647-749-0045