Gases and gas bottles
Gases and gas bottles in the laboratory constitute a particular risk both to people and to materials.
Before starting to use gases and gas bottles inside buildings and laboratories, dispensation must be obtained from the Bergen Fire Service.
- A person responsible for the gas equipment should be appointed, and a log should be filled out for every service.
- Avoid taking bottles into the laboratory where possible.
- If you need to use gas, use the smallest quantity necessary.
- Labelling of laboratories in which gas bottles can be found.
- To protect against contamination, a residual pressure of 1.5–2 bar must always be maintained in the gas bottles.
- During transportation, a bottle trolley should be used and a bottle cap fitted.
- Do not throw or crush the bottles or subject them to knocks or shocks. Handle them with care and respect.
- Do not lift or release them by the valve cap.
- Do not bring them into contact with oils, fats or chemicals.
- Bottles must always be moved and stored with the bottle cap and, where applicable, acorn nut fitted.
The units must have procedures for performing particularly high-risk work operations.
Flammable gas must be stored in cupboards that ventilate to air. Remember also that the hose from the back pressure valve must be taken into fresh air. Gas bottles containing flammable gas and bottles containing non-flammable gas must not be stored together (minimum distance: 5 metres). All gas bottles must be secured, for example by chaining them to a wall. When using gas bottles inside buildings and laboratories, an application for dispensation must be submitted in advance to the Bergen Fire Service.
- Regulators, back pressure valves and flame arresters attached to the gas bottle must be designed for the gas in question. (For example, only hydrogen equipment should be used for hydrogen gas, etc.) The equipment must also meet the demands of the instruments and analysis in terms of cleanliness and quality.
- Safety valves for flammable or toxic gases must be equipped with a hose or pipe that leads to fresh air. (Such valves should also be used for oxygen.)
- All equipment must be kept clean and free of contamination, and regular inspections and maintenance should be performed. The inspections should also include hoses, pipe junctions and “end fittings”.
- Industrial gas regulators must be serviced or replaced every 5 years.
- High-pressure hoses with synthetic inner tubes must be replaced every 5 years.
- High-pressure hoses with a steel braid inner tube must be replaced every 3 years.
Containers for deep-cooled gas
- All containers used for cryogenic gases must be of a special type, double-walled with an insulating gap.
- Due to large evaporation from cryogenic gases, they must be stored in well-ventilated rooms.
- When handling, one should use protective equipment such as a face shield, solid loose-fitting gloves and tight-fitting footwear.
- Transport of containers with deep-cooled gas in an elevator poses a danger with regard to suffocation due to evaporation. Be 2 people, and send the container alone in the elevator, preferably with a sign "I travel alone" on the container.
- Liquid nitrogen is usually stored without pressure. Such a container often consists of 2 containers with a vacuum in between. The containers are fragile and should therefore not be lifted to fill each other. Instead, use special tapping heads. In the event of a leak between the 2 containers, you will typically get a visible ice formation on the outside of the container.
- Pressurized cryo containers must be checked every 5 years.
- Remember that liquid nitrogen expands in gaseous form, 1 l of liquid nitrogen becomes 700 l of gas.
Dry ice is CO2 in solid form. It is colorless, has no odor, and has a temperature of -78 C and can thus cause frostbite on skin contact. Dry ice sublimates (evaporates) directly to CO2 gas which displaces air and can lead to suffocation. At room temperature, 50-60% of the dry ice will sublimate within 1 day. In a freezer (-20 oC), 25-30% of the dry ice sublimates in one day.
Therefore, never buy large quantities of dry ice that is stored in freezers / freezers / cold rooms. Buy small quantities, and store the dry ice in a well-ventilated room (exhaust).
All transport of dry ice by car must take place in a car with a separate cargo space.
Gases and gas bottles in the laboratory constitute a significant risk both to people and to materials. Dispensation must be sought from the Bergen Fire Service for all gas bottles inside buildings and laboratories before use.
Pressure, pressure increase (explosion)
- Common to all gases is that uncontrolled heating can lead to a major increase in pressure, thus causing the bottle, container or tank to explode.
- Direct and uncontrolled release of pressure from a container of compromised gas can also occur without any direct heating.
- In the event of the uncontrolled release of pressure, a bottle can be sent off like a rocket.
- Gas bottles must not be stored at temperatures exceeding 45°C.
- All gases kept under pressure may be subject to an increase in pressure: hydrogen, argon, air, nitrogen, carbon monoxide, mixtures of methane (among others) in argon, to name but a few.
Fire, flammable gases
- Flammable gases will, on ignition, burn in air. These are classified as “flammable products”.
- In order for the gas to ignite and burn explosively, the mixing ratio/volume percentage of the gas and the air must lie between the LEL (= Lower Explosive Limit) and the UEL (= Upper Explosive Limit). The LEL and UEL will vary among the different flammable gases. See examples in the table
- The most commonly used flammable gases and flammable mixtures are: hydrogen, methane, propane, carbon monoxide, hydrogen sulfide, 10% methane in argon, Formier (10% hydrogen in nitrogen) and acetylene, which has a number of additional hazardous aspects. (This is not a complete list of flammable gases.)
- A colourless gas with a garlic odour.
- Acetylene requires special handling as the gas may decompose explosively and generate great heat without contact with oxygen.
- The risk of decomposition increases with increasing temperature and pressure, and further with increasing pipe diameter.
- Acetylene is supplied in special bottles filled with a porous material and solvent (acetone) in order to reduce the danger of decomposition.
- Oxygen is an absolute necessity to maintaining life. (A person performing moderately heavy work needs approx. 25 litres of atmospheric air at 21% oxygen by volume.)
- If the air is diluted by any gas other than oxygen, the oxygen content will be reduced. The effects of a reduction are as follows:
- One-half, approx. 11% by vol. – causes unconsciousness after a short time.
- At approx. 6% by vol. – causes immediate unconsciousness and asphyxiation.
- The lower oxygen content limit without the use of fresh air equipment has been calculated as 17% by volume at atmospheric pressure.
- The danger of rarefaction of the air and a shortage of oxygen is always present whenever:
- an inert gas (nitrogen, argon, helium) is used as a protective atmosphere.
- there is a leakage from the packaging.
- there is evaporation of a deep-cooled (cryogenic) gas. Deep-cooled gases produce a volume increase on evaporation at atmospheric pressure, leading to a significant danger of asphyxiation (heavier than air, difficult to ventilate).
- Gases that may lead to a danger of asphyxiation include: nitrogen, argon, helium, carbon dioxide, dinitrogen oxide, ammonia, hydrogen, methane and propane.
- Oxygen is a special case when it comes to FIRE HAZARDS.
- Colourless, odourless and tasteless gas.
- Is not in itself flammable or explosive.
- All combustion takes place faster than in air.
- Oxygen is a prerequisite for all combustion, and oxygen-enriched air (O2 conc. > 21% by vol.) will make it easier for flammable materials to ignite, while it will be possible for non-flammable materials to catch fire.
- Oxygen enrichment has no significant effect on the LEL but will normally increase the UEL, thus expanding the range in which there is an explosion risk.
- Evaporation of deep-cooled oxygen produces a significant increase in fire risk. Liquid O2 produces a large increase in volume on evaporation.
Fat/oil is incompatible with oxygen and leads to an increased explosion risk!
- Liquid, deep-cooled gases are at extremely low temperatures. Skin contact with such gases or with cooled pipes and fittings can lead to freeze injuries that are just as serious as burns.
- Low temperatures can also lead to cold brittleness and impose special requirements on the materials that can be used.
- The most common liquid deep-cooled gases are: nitrogen, helium and oxygen.
- Some gases have an asphyxiating effect even at low concentrations in air, even if the oxygen content is normal. This is due to the chemical toxicity of the gases destroying or paralysing the respiratory organs themselves, so that the body is unable to use the oxygen in the air.
- Examples of gases that are toxic are: ammonia, chlorine, carbon monoxide and hydrogen oxide. (This list is not exhaustive.)
Plans for the disposal of gas bottles must be made at the time of purchase.
- For normal use, hired gas bottles from a gas supplier should be used. Hired bottles can be returned to the gas supplier.
- This applies to bottle sizes from 10 to 50 litres (medicinal oxygen from 1 litre)
- This is because gas bottles must be pressure-tested and certified at regular, specified intervals.
- (In the case of owned bottles, the site of use at the University of Bergen is responsible for pressure-testing and certification of the gas bottles. The site of use must also bear the cost of this maintenance. The gas supplier is unable to assist with this.)
- The UiB has a framework agreement for the purchase of gas. See the Purchasing Guide.
- For gas bottles of a size from ml up to 10 litres, the user must do the following before purchase:
- Clarify possible disposal and the costs of disposal.
- The costs of disposal must be borne by the site of use. Contact the gas supplier.
- Irrespective of size, gas bottles must not be disposed of in the hazardous waste rooms at the UiB.