How dangerous is a calibration gas cylinder?

Calibration gas cylinders are considered dangerous goods but how dangerous are they? After all, most gas calibration gases are classified as “non-toxic, non-flammable” gases.

Aside from the obvious hazards associated with flammable and toxic gases, all compressed gas cylinders have associated hazards which the user should be aware of.

Firstly, it is important to understand the difference in UN DG classification and recognising dangers when using and handling cylinders. Even cylinders whose contents are classified as non-toxic, and non-flammable can be very hazardous to health.

As noted in a previous article, chlorine up to and below 2000 ppm in nitrogen is considered non-toxic and non-flammable but concentrations of 2000 ppm chlorine is very toxic (TWA: 1 ppm   STEL: 0.5 ppm). Transport classifications are based primarily on risk to human health, but they are designed to direct action in emergencies rather than provide guidance for safe usage. Always read the SDS. Relying on the transport classification is not sufficient. Gases can vary in danger, even if they are within the same UN classification.

 Calibration gas cylinders can be pressurised between approximately 3 to 300 BAR. On the outside, a cylinder filled to 3 BAR will appear the same as one filled to 300 BAR. A cylinder filled to a higher fill pressure represents a greater danger if it is damaged.

Cylinders that undergo rapid or violent decompression can become missiles. It is important not to underestimate the potential damage a venting cylinder can cause. Under the right conditions cylinders can pass through walls or cause other severe damage.

It is highly unlikely for a cylinder to undergo explosive decompression without having suffered external damage. Take care to secure your cylinders in place using mounts; never leave cylinders where they can be knocked over, especially where there is potential for the valve to contact another object if it were to fall; be careful when moving cylinders; and when storing cylinders, ensure the protective valve cap is installed. CAC Gas supplies a wide range of cylinder handling and storage products to keep workers safe.

Some cylinders are upwards of 70 kg with a small base to stand on. If a cylinder topples do not attempt to catch it or steady it as serious injury may occur. 

Gases cool when they decompress, and temperatures can reach damaging levels if the decompression is rapid enough. If the cylinder contacts skin, cold burns can result.

If you have a cylinder which is quickly decompressing do not attempt to touch the cylinder until sufficient time has passed to allow the cylinder to come back to ambient temperature.

 Although gas cylinders should not be left in direct sunlight, heat from sunlight alone will not cause your cylinder to explode. Calibration gas cylinders typically have working pressures at about half the burst pressure rating. To reach the burst pressure the cylinder would need to be exposed to extreme temperatures, such as in a fire.

Some cylinders are equipped with a pressure relief device. This device is designed to vent cylinder contents before the cylinder reaches burst pressure. It is conceivable that naturally occurring heat (such as strong sunlight on a hot day) could cause venting of cylinder contents.

If you are unsure if your cylinder has a pressure relief device, contact CAC Gas.