Is Brake Cleaner Toxic? What the SDS Actually Says

What Is Brake Cleaner?

Brake cleaner is the aerosol you reach for during a brake job. You spray it on rotors, calipers, and pads to blast off grease, brake dust, and the oily film left by fingers, then it flashes off fast and dries without a residue. Mechanics also use it as a general parts solvent for anything that needs to come out of the shop spotless.

Here is what most people never notice at the shelf: "brake cleaner" is two completely different chemistries wearing similar-looking cans. One is chlorinated, one is non-chlorinated, and their Safety Data Sheets could not be more different. They clean about the same. What changes underneath is the hazard you are holding.

What the Safety Data Sheet Says

These verdicts come from the hazard codes and GHS classifications in the manufacturers' Safety Data Sheets, not from CarCareTruth's opinion. Brake cleaner splits into two chemistry types, each with its own SDS profile.

The chlorinated type is built on perchloroethylene, often called perc. Its SDS carries a health-hazard profile: H351 (suspected of causing cancer), H332 (harmful if inhaled), H315 (skin irritation), H319 (serious eye irritation), and H336 (drowsiness or dizziness), plus the environmental codes H411 (toxic to aquatic life) and H420 (destroys upper-atmosphere ozone). It is not flammable, which is the one thing it has going for it.

The non-chlorinated type removes perc and rebuilds the formula on acetone and heptane, sometimes with toluene or methanol. That swap deletes the cancer and ozone flags but adds a big one: the SDS classifies it as H225 (highly flammable liquid and vapor). It still lists H304 (can be fatal if swallowed and it enters the airways) and H336 (drowsiness or dizziness). Both aerosol types also carry H280 (contains gas under pressure) from the propellant.

GHS Hazard Classification

The label tells you most of this at a glance. Chlorinated brake cleaner carries a WARNING signal word and the health-hazard symbol driven by its cancer flag, with no flame. Non-chlorinated brake cleaner carries DANGER and the flame symbol, because H225 flammability is a higher-tier physical hazard. Two codes anchor the split: H351 for the chlorinated cancer risk, and H225 paired with H304 for the non-chlorinated formula. Neither can is harmless, but they fail in opposite ways.

Key Ingredients

The chlorinated formula's whole profile comes from perchloroethylene, a probable human carcinogen (IARC Group 2A) that is also ozone-depleting and persistent in water. Some older or imported chlorinated formulas used dichloromethane (methylene chloride) instead, which carries the same 2A cancer classification and has caused deaths in enclosed-space use. The non-chlorinated formula is built on acetone and heptane, fast-evaporating solvents whose main hazard is flammability and narcotic vapor. Some add a little toluene, which is Prop 65 listed for reproductive harm, or methanol, which is toxic if swallowed and can cause permanent blindness or death even in small amounts. The aerosol propellant is usually carbon dioxide, which is inert but stores the can under pressure.

What Sections 8 and 11 Say About Exposure

The gear each SDS calls for tracks its chemistry. Both types get chemical-resistant gloves in Section 8, because both are strong degreasers that defat skin and perchloroethylene can absorb through it. Nitrile is the practical glove, since these solvents pass through thin latex quickly. Both get eye protection for the spray-back. Ventilation is where they matter most: for the chlorinated type it limits inhalation of a carcinogen (H332), and for the non-chlorinated type it clears flammable vapor before it can find a spark. A respirator is not a blanket requirement here, but it moves from optional to worth considering when you must use the chlorinated formula in an enclosed space with poor airflow, because that is the scenario where carcinogen vapor concentrates. Across both types, a closed garage is the setting that turns a manageable job into a real exposure.

The Main Risk Pathways for Car Owners

For a home mechanic, the hazards line up in a specific order. Inhalation comes first. You spray a fast aerosol at close range, the mist drifts back at you, and the vapor that causes drowsiness (H336) and, for the chlorinated type, the carcinogen exposure (H351) climbs quickly in a closed space. Fire is the other headline risk, and it belongs to the non-chlorinated type. It is a highly flammable liquid and vapor (H225), so a pilot light, a water heater, a grinder throwing sparks, or a hot exhaust manifold near the spray is a genuine ignition hazard. Skin is third. Both formulas strip the oils out of skin on repeated contact, and the chlorinated type adds skin irritation (H315) and skin absorption, which is why gloves are in the SDS.

Pets and kids face the swallowing and contact risks. Brake cleaner is harmful if swallowed (H302), and the non-chlorinated type carries an aspiration danger (H304), meaning a pet or child who swallows it and then chokes can pull the liquid into the lungs. If someone swallows the non-chlorinated type, do not induce vomiting, because bringing it back up is exactly how it reaches the lungs. Store the can sealed and out of reach, and clear the work area before you spray. If a pet swallows any, call your vet or the ASPCA Animal Poison Control Center at 888-426-4435.

What the SDS Does NOT Flag

A few common fears do not show up in the hazard data for typical brake cleaners. Neither type is classified as a respiratory sensitizer (no H334), so brake cleaner does not cause the asthma-type reaction that some coatings and two-part chemicals do. Neither is corrosive to skin (no H314); these are degreasers that dry and irritate skin, not acids or strong bases that burn it. And the flammability of the non-chlorinated type is a physical hazard, not a poisoning one: a flammable liquid is a fire risk, which is a separate thing from toxicity. Naming what the SDS does not classify matters as much as naming what it does, because absence of a code is not the same as a clean bill of health, only the absence of that specific classification.

The Two Chemistries: Chlorinated vs Non-Chlorinated

Brake cleaner is the clearest example in the garage of two products doing one job with opposite risk profiles, and the split is worth understanding before you buy.

The chlorinated formula is dangerous slowly. Perchloroethylene is a probable human carcinogen (IARC Group 2A), listed under California Prop 65, and an ozone-depleting substance (H420). It is not flammable, which is why it was popular for decades: you could use it near sparks. But that same chlorine chemistry hides a sharp acute hazard. When perc is exposed to the extreme heat and ultraviolet light of a welding arc, it decomposes into phosgene, the poison gas used as a weapon in the First World War. The CDC notes phosgene can form when parts cleaned with chlorinated hydrocarbons are welded, and OSHA holds the workplace limit to just 0.1 ppm. This is the real basis for the shop rule that you never weld after using chlorinated brake cleaner.

The non-chlorinated formula is dangerous fast. Built on acetone and heptane, it is a highly flammable liquid and vapor (H225) with an aspiration hazard (H304), but it carries no carcinogen code and does not form phosgene. It swaps a slow chronic risk for an immediate fire risk that you manage with ventilation and by keeping flame away.

Regulators forced the shift. California's Air Resources Board has prohibited brake cleaners containing perchloroethylene, methylene chloride, or TCE from being sold in the state since June 2001, and the US EPA has moved to ban most remaining consumer uses of perchloroethylene as a cancer risk. That is why the non-chlorinated can is now the default on most shelves, and why the chlorinated can, where it is still sold, is the one that carries the heavier chemistry.

Safer Choices and Product Context

If a choice exists on the shelf, the non-chlorinated formula is the lower-hazard pick on health and environmental grounds. It removes the probable-carcinogen solvent (perchloroethylene) and the ozone-depleting classification (H420), which is why it is the version sold nationwide and mandated in California. The tradeoff is flammability, so it is used away from any ignition source and with airflow, never in a closed garage near a pilot light. There is no version of brake cleaner that carries no hazard at all; the honest move is to pick the flammability risk you can control over the cancer risk you cannot see.

Brake cleaner is usually the first step in a larger brake job. If that is what brought you here, our brakes department covers the parts that follow: brake pads and brake rotors, each graded on the CCT scale for effectiveness and health impact.

Sources and SDS Reference

• GHS hazard classifications and H-codes for the two chemistry types are drawn from the published SDS profiles of the dominant brake-cleaner issuers (CRC Brakleen chlorinated and non-chlorinated, Gunk, Permatex, WD-40 Specialist) and cross-checked against CarCareTruth's own ingredient chemistry pages.
• Perchloroethylene chemistry, IARC Group 2A classification, Prop 65 status, and ozone/aquatic codes: see our perchloroethylene ingredient page. Methylene chloride cancer classification and enclosed-space fatalities: see our dichloromethane page.
• Phosgene formation from welding on chlorinated-solvent residue, and the 0.1 ppm workplace limit: CDC/ATSDR ToxFAQs: Phosgene.
• California phase-out of chlorinated brake cleaners: California Air Resources Board Airborne Toxic Control Measure for Automotive Consumer Products. Federal perchloroethylene restrictions: US EPA.
• CarCareTruth ingredient and hazard-code pages, and the SDS database for looking up a specific product's sheet.