# Compressed gases

Compressed gas cylinders combine a physical property, high pressure, with chemical properties which depend on the nature of the gas.

Refer to the safety data sheet (SDS) for information about the hazards of a particular gas.

The main hazards related to compressed gases are:

##### 1. Physical hazard: high pressure

The filling pressure of compressed gas cylinders can be up to 300 bar: there is a danger of burst or rupture due to pressure. As temperature rises the pressure in compressed gas bottles rises as well, strongly increasing the risk of explosion. This is particularly important for liquefied gases as propane or butane. The gas can be ejected accidentally in case of a valve or other safety device deficiency.

##### 2. Chemical hazard: type of gas
• Inert
• Flammable
• Oxidant
• Toxic or Corrosive

A single gas can combine different chemical properties: hydrogen sulfide (H2S) is toxic, corrosive and flammable.

You can check the chemical hazard symbols on our chemical hazards page.

According to the internal directive on the storage of gas cylinders (LEX 1.5.6, PDF), the quantity of gas allowed in a lab depends on the type:

• Inert gas: maximum 4 cylinders with 2 Nm3 in total per lab
• Flammable or oxidizing gas: maximum 2 cylinders with 0.6 Nm3 in total
• Toxic or corrosive gas: maximum 2 cylinders with 0.2 Nm3 in total

You can calculate the Nm3 (normal cubic meter) for your cylinders by applying the following formula:

p = pressure of the cylinder in bar

V = volum in liters

Never drag, slide or roll a gas cylinder.

To transport a gas cylinder safely, you should follow 4 simple steps:

1. Get a three-wheeled cylinder cart
2. Remove the regulator and put the protective cap
3. Secure the cylinder to the cart.
4. While moving: hold the cylinder with one hand on the safety cap and hold the cart with the other hand.

### Full gas cylinders

When a cylinder is not used, always put and close the protection cap on it in order to protect the main valve.

When storing full gas cylinders, the following rules apply:

Cabinets: all gas cylinders should be stored in fire proof cabinets (EI90). For flammable, corrosive and toxic gases the cabinet must be ventilated.

Location:

• Gas cabinets are normally stored outside the lab. Toxic gases only are preferably stored inside the lab to keep the hazard localised.
• Do not keep pressurized gas cylinders near heat sources.

Detectors:

• Inert gases: oxygen deficiency and CO2 detectors are installed inside the lab if necessary.
• Toxic, corrosive or flammable: gas detectors are installed inside the labs and inside the cabinet.

Signalization: blinking signalization is installed on the door of the lab (both sides), to alert users of:

• the lack of oxygen
• the leak of hazardous gases

Gas Cylinder fixing: A gas cylinder must be secured at all times to a fixed location (a wall, a non-transportable piece of furniture, etc.):

• at 2/3 of its height using a chain or gas cylinder straps
• one bond per cylinder

Connectors and regulators:

• Adapters of any kind are forbidden.
• Make sure the cylinder is equipped with the correct and certified regulator for the specific gas used. If you have any doubt about it, contact your gas supplier.

### Empty gas cylinders

Never empty the cylinder completely, always leave a residual gas pressure of at least 2 bars.

Remember :

• Return the empty bottles to the supplier before their expiration date.
• Empty and full bottles must be stored separately; empty bottles should be clearly marked, with the valve closed and protected.

### Leaking gas cylinders

Store leaking gas bottle in open air, if inert or in an artificially ventilated space otherwise. Mark it as leaking and inform the gas supplier.

## Gas Safety Measures

Safety tips on gas cylinders usage

##### Before the first use

Make sure the cylinder is equipped with the correct and certified regulator for the gas in use. If you have any doubt about it, contact your gas supplier.

Read the safety data sheet for handling and safety information about the gas you are using. In this document you will find protective equipment to use while handling the gas. If you still have any doubt regarding the gas handling, you can contact us.

##### General use

Never refill a cylinder by yourself: mixing of residual gases in a confined area may result in serious and devastating reaction.

Open the valve slowly, without abruptness, and completely. Never leave a valve partly opened. Close the valve when there are long interruptions between use and remove the pressure regulator.

Never use grease or oil on the regulator or cylinder valves: these substances may cause an adverse, dangerous reaction with the gas contained in the cylinder.

Never use oxygen as a replacement for compressed air.

## Special protective measures

Hydrogen
In order to reduce the hazards, for pressures below 10 bars the hydrogen is produced directly in the lab using hydrogen generators (by water hydrolysis). Ask your safety delegate (COSEC) or send us an email at [email protected] for details.
Carbon Dioxide
CO2 is under detection when the concentration in the lab can reach or surpass the limit value of 5000 ppm (ml/m3). Send us an email at [email protected] for questions or details.
Toxic and flammable gases
Depending on their quantities, toxic and flammable gases can be subject to detection in the lab as well as inside the storage cabinets. In case of a leak, the detection interrupts the gas distribution and send an alarm to the Centralized Place of Command – PCC (from French ‘Poste de Commande Centralisé’).

If your laboratory is using gases under detection you have to be familiar with the alarm management procedures developed jointly by ‘Domaine Immobilier et Infrastructures’ (DII) and your unit.

## In case of gas leak:

Call the emergency number 115 or +41 21 693 30 00 Alarm (unless the automatic alarm hasn’t already been activated) and evacuate people in danger if possible – Only equipped and trained personnel can be involved in emergency action. If a cylinder has been dropped and seems to be damaged, do not use it anymore and return it to the supplier.