Safety Services


Gases - compressed

This guidance is intended to increase awareness of the risks and the precautions to be taken when using compressed gas and handling compressed gas cylinders.

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What are the risks of compressed gas?

Compressed gas sign
In order to assess the risk of working with compressed gas, its important to consider the ways that gases can accumulate or be released into air within the workplace. They include leaks or releases as a result of:
  • damaged or poorly maintained hoses, pipes and valves;
  • poor connections;
  • accidentally opening valves;
  • not closing valves properly after use;
  • poorly ventilated work areas.

The consequences of leaks or releases will depend on the hazardous nature of the gas but in general they are:

  • explosion e.g. release of flammable gas can create an explosive atmosphere
  • enrichment e.g. increase of carbon dioxide can result in asphyxiation
  • depletion e.g. increase of nitrogen leading to a decrease in oxygen leading to asphyxiation

NB Some gases have more than one hazardous property; for example, carbon monoxide is toxic and flammable.

Other risks can result from:

  • poor manual handling technique causing injury to the operator or damage to the cylinder resulting in the release of high-pressure gas;
  • over pressurisation of some experimental chambers where an inert gas is used as a purge. In these circumstances, a pressure relief valve must be incorporated into the experimental set-up.

The destructive potential from the uncontrolled release of gas should not be underestimated.

Safety data sheets

Safety data sheets provide information that helps users to make a risk assessment and these should be available at the point of use or storage. They describe the hazards and give information on the handling and emergency measures in case of an accident.

In addition, the safety data sheet provides information about storage, particularly segregation e.g. gases that are incompatible and shouldn't be stored together like oxygen and acetylene.

More information on Safety Data Sheets


Managers must:

  • supervise those with least experience until competency has been gained;
  • intervene and stop work if there is any variance to agreed procedures.


Restricted access sign
Managers who supervise work or processes which involve the use of compressed gases must be competent (through training and experience) to do so.

Anyone who uses compressed gases should be given information about the risks and instructed in gas cylinder safety.

Instruction should include:

  • moving cylinders safely;
  • connecting regulators and hoses;
  • pre-use checks of cylinder and attachments.

Record keeping

Records should be kept of the information, instruction and training that individuals have received.
Instructions and procedures must be documented in the form of safe operating procedures, arrangements for safe working or codes of practice.

Health and safety inspection

Managers must ensure that areas, where compressed gases are used and stored, are inspected periodically to ensure the effectiveness of risk control measures.

More information on Monitoring - Health and Safety

Gas cylinders

When compressed gas cylinders are introduced into a work area or building for the first time e-mail fire@ucl.ac.uk with details of the type of gas, a number of cylinders and the location where they will be used and stored. This information will be used by the Fire Safety Team to update the fire and rescue information packs available in the Premises Information Box.

Using gas cylinders

Whenever possible, select the smallest size of gas cylinder available. When siting gas cylinders in the workplace, make sure that:

  • they are supported with chains or straps in an upright position;
  • they are protected from mechanical damage and sources of heat;
  • the gas supply is turned off at the cylinder when not in use;
  • the area where the cylinder is used is well ventilated;
  • oil, grease or jointing compound is NOT used on cylinder fittings.
Moving gas cylinders

If possible, arrange to have gas cylinders delivered to the point of use. If this is not possible, make sure that:

  • anyone moving cylinders is trained to do it safely;
  • a trolley is always available to move cylinders from the storage area to the work area;
  • personal protective equipment is worn to protect feet and hands. 
  • gas cylinders are never moved with the valve open.
Storing gas cylinders

Cylinders should ideally be stored outside the building. If this is not possible, the number of stored cylinders should be kept to a minimum.

  • Access to cylinder storage areas should be restricted to authorised people only. The storage area should be well ventilated and cylinders should be stored in the following way:
  • support the cylinders with chains or straps in an upright position;
  • empty cylinders should be labelled 'empty' and stored separately from full ones;
  • segregate gases according to type and compatibility (refer to the safety data sheet if in doubt).
Gas regulators

Gas Regulator
Gas regulators are designed to reduce the pressure of the gas from the cylinder to the lower pressure required for the operation of the equipment or process.

Regulators typically have the following features:

  • inlet pressure gauge which indicates the pressure in the cylinder;
  • delivery pressure gauge which indicates the reduced pressure being delivered to the equipment or process;
  • a pressure adjusting valve which controls the volume of gas entering the gas delivery gauge.

The gas regulator must be selected for use with the gas it was designed for - they are not interchangeable! Using the wrong regulator can damage it or result in a serious accident.

NB Gas regulators are precision instruments and can be easily damaged - treat them with care!

Inspection, testing and replacement of gas hoses

Gas regulators should be:

  • regularly inspected to confirm they are free from damage or contamination;
  • tested and inspected annually by a competent person to ensure they are functioning correctly. BOC carry out the annual test and inspection on behalf of departments;
  • replaced at least every 5 years whether they have been used or not because they contain parts that deteriorate with time.
  • Managers responsible for the work with compressed gases must ensure that regulators are inspected, tested and replaced at the intervals specified.

Never attempt to alter or repair gas regulators or valves.

Gas hoses

The condition of the hoses used to connect the cylinder to the equipment is vitally important to safety.

Hoses should:

  • be protected from mechanical damage, heat, sparks, oil and grease;
  • not be longer than needed and they should not be kinked or twisted;
  • be replaced if they show any signs of damage and therefore must be visually inspected frequently;
  • be compatible with the gas with which they are to be used;
  • be used at the pressure for which they are designed.

Always use:

  • pressure hoses to connect gas cylinders to equipment;
  • retaining clips or ferrules to secure hoses to gas cylinders and/or equipment.
Cylinder signage

Doors to areas where compressed gas cylinders are used and stored should display hazard warning signs indicating the presence of compressed gas cylinders and any additional hazard associated with the type of gas e.g. flammability. This information is essential to fire and rescue personnel when carrying out operations. Fixed pipes should be labelled so the gas content of the pipe is clear.

Guidance on signage

Last updated: Wednesday, July 15, 2020