H&S Dangerous Gases

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Brake Cleaner (chlorinated)

Phosgene (WW1 trench chemical warfare gas) can be produced from un-evaporated Brake Cleaner +Plus+ Heat. With Argon (e.g. MIG/TIG welding)as well, phosgene can flash off and incapacitate you in seconds! No joking, lethal, no hospital can treat it!

It smells of cut hay, or fresh grass... usually for those that smell it, it's too late to avoid some permanent damage, if not death.

Brake Cleaner Dangers - a personal experience

Read the back of the can.. if it says chlorinated then make sure you know what NOT to do with it... no heat and no other rare gases.

If in doubt Carb Cleaners (generally) are chlorine free, but check..

Be cautious of all solvent cleaners and paints of course, re: noxious fumes, esp.

Freon (refrigerant)

combined with combustion products can produce phosgene!

Quote from general links below

Been exposed to phosgene twice without really knowing what it was and yes it is very, very bad stuff. One time years ago when we simply drained refrigerant without recovering it I was draining an auto a/c and left the hoses under the hood while I pulled the car into the shop. Simply letting the Freon near the air inlet was enough. Walked by the rear of the car and my lungs froze up. Other time was also draining Freon near a salamander type heater.

Lucky to live I guess.

Electrical Switch/Contact cleaners

Good electrical contact cleaners (chlorinated ones) can also produce this phosgene gas

Generally, if a solvent flashes off clean, removing contaminants, it could well be dangerous used inappropriately

Fire Extinguishers

The worst fire extinguishers for phosgene were the Halon / Carbon Tetrachloride ones.

40 years ago, Navy, we had a foam dispenser aboard ship for oil fires, Diesel boat. Were told that using the foam would create Phosgene gas when it hit hot metal.

Hydrofluoric Acid

Overheated Teflon (PTFE)

Supposedly 450F is the point at which this gets dangerous.. sounds very close to what is achieved in normal bacon and eggs type cooking, or when non-stick frying-pan left on with nothing in it.

Teflon is also a baddie. When heated above 500deg F or so, it can emit dangerous gas. I personally spoke to the guy who discovered this little factoid while working for a nuclear plant. They used to think Teflon was great stuff until this was known.

Your Teflon coated cookware can do this if you leave an empty pan on a burner for a few minutes. Since that time, I've looked specifically for non-coated cookware.

The bad stuff from overheated teflon (PTFE) and the other fluorinated plastics (eg in high temp 'O' rings) is hydrofluoric acid, not phosgene.

HF is well capable of penetrating through gloves and then through your flesh. By the time you feel tingling the damage is done, and that flesh and bone will probably die, once it does start to hurt, the pain is supposed to be out of all proportion to the size of the affected area.

As a gas, it will not only burn your lungs but will also react with calcium in your body, potentially causing a heart attack.

Car fires (putting the fluorelastomer myth in context)

To balance the rumours about overheated fluoroelastomers (specifically viton type seals in car fires) the following HSE publications are well worth reading:

Fluorelastomers in fires 1 (correcting the rumours)

Fluorelastomers in fires 2

Thanks to CycloneMike for pointing us to these two relevant publications

Some car wheel cleaners and passivating solutions

HF (hydrofluoric acid) is an ingredient of some of the passivating solutions for cleaning stainless, and the solutions for cleaning car wheels and windscreens. Lovely stuff. Not!

Welding and brazing fluxes

Some welding and brazing fluxes contain fluorides. Exposing them to sulphuric acid will liberate HF (sulphuric acid displaces (almost) all other acids from their salts)

Dry Cleaning Solvents

Dry cleaning solvents are all bad when overheated, a poster on a british HSM board gave an example of almost gassing himself when he poured CCl4 on a wastebin fire in his workshop.


Oxy/Acetylene welding

Oxygen, is of course a strong oxidising agent. The acetylene provides the hydrocarbon fuel. Fat, oil or grease (hydrocarbons) must never been used in an oxygen rich environment, spontaneous combustion can occur. Most professionals will know this, but is worth anyone around this type of equipment knowing. Greasy hands when opening valves on an oxygen bottle, blasting the nozzle clean by opening the cylinder valve when grease/oil are present etc


Zinc plated steel (Galvanised)

Welding through galvanising can produce dangerous fumes. Ditto heating lead products. Ditto some etch-primers and othjer metal treatments. These are not in the Phosgene, HCL deadly class , nor produce long term incapacitation, but shoul;d be avoided all the same. Heavy metals are toxic, don't inhale welding any gases and wash your hand after handling lead/zinc etc. Not a bad idea to wear thin gloves if working glav materials.

Don't smoke in a welding environment

Symptons of zinc or lead fume inalation can be flu like, sickness, vomiting, nausea, depression, edgy, easily niggled, tired etc

Here is some discussion, with varying viewpoints

Other dangers

Please read this whole H&S topic

..which contains several references to dangerous gases that can be produced when welding, MIG, TIG especially but also dangers of Oxy/Acetylene. The most dangerous is Phosgene, so read those items 1.1. 1.2 etc.

Solvents, Adhesives and Paints

Be cautious of all solvents, cleaners, adhesives and paints of course, re: noxious fumes and skin contact.


Lung damage and breathing difficulties (some fumes may not be readily smelt or recognised)

Loss of situational awareness (drowsiness)

Fire & explosion (ignition sources such as static electricity as well as mixing pouring etc)

Skin problems (dermatitis especially related to solvents in industry)

Never wash your hands with solvents!

As far as possible work outside with solvents, capping before returning to safe storage.

One big danger with solvents is that they can cause trouble before you realize what’s happening. Depending on the type and concentration of the solvent, exposure effects can range from mild respiratory irritation to severe damage to body organs and systems. In extreme cases, overexposure to solvent vapors can cause respiratory failure and death.

Solvent Dangers

General links on gas, fume and toxic dangers (vehicles/workshops)

Forum posts on such dangers

Solvent Dangers

Fluorelastomers in fires 1 (correcting the rumours)

Fluorelastomers in fires 2