Is Acetylene Flammable? (Answered)

Welding involves joining two metals together by applying heat, pressure, and filer separately or in any combination, and acetylene is the most common fuel for welding torches.

In other words, burning acetylene emits excess heat that you can use it to join metals effectively. But is acetylene flammable?

Acetylene is a highly flammable gas that can burn when it reaches -0.7 degrees Fahrenheit, equal to -18.5 degrees Celsius. So, it is important to take adequate care while using or storing it.

Whenever you are using gas as flammable as acetylene, you must understand what it means and how it works; doing so will make you a lot safer.

What Is Acetylene?

First used in 1906 for welding and chopping metals, acetylene is a colorless hydrocarbon gas with a pungent smell. It burns with a bright flame and is widely renowned for being the most powerful yet the safest and easiest to use of every fuel gas.

The welding activity that involves acetylene is called oxy-fuel cutting or gas cutting.

One of the unique features of acetylene is its combination with oxygen (oxy-acetylene) to give rise to a flame temperature of about 3150 degrees Celsius.

This makes it the hottest fuel gas present and the one fuel gas capable of welding steel and used for heat-treating metals and other tools.

When you use it to cut, acetylene offers the quickest preheating and piercing times of every other fuel gas combination.

It also offers the lowest rate of hardening to the surface of the cut, and since lower heat rates are transferred into the item being cut, misshaping is greatly reduced.

Ethyne (another name for acetylene gas) functions with lower oxygen than other gases, including propane and propylene, and needs fewer cylinders, with careful handling and downtime.

Acetylene gas is a little bit lighter than air. This prevents the unused gas from gathering in low areas, thus creating a potential hazard.

How Dangerous Is Acetylene?

Acetylene is seen as a very hazardous chemical to work with. It is unstable chemically. It can easily combust, and you must be careful with how you move and transport it.

If you work with acetylene in welding and other workshops, you must be properly trained and adhere to all health and safety precautions.

Acetylene is very risky if you use it under the wrong conditions; hence, you ensure that those situations never arise.

Is Acetylene Flammable?

Acetylene has a flashpoint of around -0.7 degrees Fahrenheit (-18.15 degrees Celsius), which is very well below its normal 199.4 degrees Fahrenheit (93 degrees Celsius) top limit for flammable substance. In other words, acetylene is highly flammable.

What Temperature Does Acetylene Burn With Oxygen At?

Immediately acetylene begins to burn with oxygen; things start getting hotter a bit faster. In its natural air mixture, where oxygen and other gases exist, acetylene burns at a temperature of about 4000 degrees Fahrenheit (2200 degrees Celsius).

It is an ideal temperature for welding aluminum or repairing a radiator. But not to the extent where you can weld steel together.

In this case, you require a pure supply of oxygen that will burn with acetylene at the flame-producing temperature of about 5730 degrees Fahrenheit (3166 degrees Celsius).

This condition clearly explains why acetylene is seen as a very hazardous gas. It is because it doesn’t only combust very easily, but also once it contacts flames, it tends to burn so fiercely.

What About Without Oxygen?

In a more dangerous circumstance, if you store acetylene for a long time, it can start breaking down into smaller parts, namely carbon and hydrogen, and will begin to emit heat as a result.

Precisely, it is capable of emitting enough heat that will cause it to ignite even if oxygen is not present, thus making acetylene almost peculiar, as it doesn’t need oxygen to combust.

At What Temperature Does Acetylene Become Unstable?

As we earlier discussed, acetylene doesn’t require any nearby flame or heat source to catch fire. As long as there is a temperature of about 763 to 824 degrees Fahrenheit, it can automatically ignite.

Since it is a very high temperature, it doesn’t require any nearby flame or fire source to burn.

However, when acetylene is being compressed during storage, the acetylene will auto-ignite at room temperature once the pressure gets to 30 psi.

So, it would be best to be mindful of storing free acetylene in high-pressure cylinders. Pumping it inside a cylinder that features acetone is much preferable, as it will absorb the acetylene.

But, don’t forget to keep the cylinder upright to prevent the separation of acetone and acetylene, which might result in a hazardous situation.

Again, do not freeze the cylinders, as acetone may be the first to be released, clogging any regulators and leaving a substantial amount of acetylene inside, which is also risky.

Is Acetylene Volatile?

Technically, acetylene is not volatile (explosive). However, due to the force of the reaction and an extremely low ignition point, you can consider acetylene reactions very explosive, especially if it gets beyond control.

Can Acetylene Tanks Explode?

An acetylene tank can explode if it passes 39 psi (kPa). A good number of acetylene tanks are low-pressure canisters.

Yet, once the acetylene combusts and starts heating an acetylene tank, it will cause the pressure to quickly increase courtesy of the highly heated acetylene flame, and they will easily go beyond 39 psi.

Is Acetylene Harmful for the Environment?

Given its safety measures, you will expect acetylene to be unfavorable for the environment, but the reverse is the case.

The gas will hardly build up in real concentrations without catching fire, and in extremely low concentrations, it’s neither toxic nor harmless to the environment like an air pollutant. 

Can Acetylene Set Off a Carbon Monoxide Detector?

A carbon monoxide detector is a very important piece of fire safety tool used in many homes and offices. While carbon monoxide is a colorless and odorless gas, it can permanently suffocate you by sticking to your red blood cells in the areas where oxygen naturally bonds.

Annually, in the U.S alone, almost at least 430 people die due to carbon monoxide effects, and over 50,000 get treatment for it.

A carbon monoxide detector is an electrical sensor mechanism that probes carbon monoxide and then initiates several symptoms if the deepest level of carbon monoxide is violated or ruptured.

Sadly, like several other gases, acetylene can set off a carbon monoxide detector. In other words, it will cause the detector not to function efficiently in an area where acetylene is constantly used.

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