'Sniffing' is the term commonly used to refer to a range of ways of inhaling a variety of volatile vapours. It is a bit of a misnomer as the vapours are more often breathed in through the mouth rather than sniffed in through the nose.

What is sniffed?

Vapours are given off by solvent based glues, petrol, paint thinners, industrial and dry cleaning solvents, gases such as butane and can also be found in a variety of aerosols, fire extinguishers and other products. It has been estimated that the average household contains at least half a dozen sniffable products.

How are they taken?

If the product comes in a tin or jar the contents are usually emptied into a plastic bag which is then placed over the mouth and nose. The vapours are inhaled by breathing or panting in a repetitive way. On occasions the glue or solvent is placed on a rag or can be sniffed direct from the container. Sometimes in the case of aerosols and gas cannisters the contents are sprayed directly into the mouth.

How are they absorbed?

The chemicals enter the bloodstream via the lungs in much the same way as drugs absorbed by smoking. See the animation on the right for more detail. This is an efficient method of getting psychoactive chemicals to the brain and the effects are felt within seconds.

What are the risks?

There are risks from the products themselves, from the techiques used in taking the products and from the situation of use.

The product specific risks arise from the exceptional hazards of some of the products. Thus although most solvents are flammable there is a particular fire risk with butane. In the same way there are specific toxic risks associated with the use of some fire extinguishers and the contents of some aerosols.

As the volatile vapour being sniffed is the propellant - most often butane - it follows that any aerosol with a volatile propellant can be sniffed for its psychoactive effect. Some such aerosol products can include for example oven cleaner.

The technique specific risks relate to the methods used to get the chemicals into the bloodstream. If the product is sniffed from a rag there are possible problems of contact sores around the nose and mouth. Many of these substances are solvents and can have a damaging effect on the skin.

Other technique risks are involved when aerosols and cannisters are sprayed directly into the mouth. The freezing cold stream of vapour hits the back of the throat and can freeze the topmost parts of the respiratory passages, in some cases causing death.

If the substance is placed in a plastic bag prior to sniffing there have been cases of young people trying to improve the effect by putting their heads right inside large plastic bags. This is always dangerous but the risks are increased by the intoxicated state of the sniffer.

Finally the situation specific hazards of sniffing arise from the settings in which the sniffing takes place. Sniffers often seek out isolated places where they will not be observed by 'interfering adults'. Many of these places are inherently dangerous. Thus railway embankments, canal sides, river banks, building sites and the tops of high rise flats have all been used by sniffers. These are not good places to be in for intoxication. These risks are made much worse when the sniffer goes off alone.