1. What are they?
Fumes are given off by substances when processes are being carried out on them (e.g. when they are being heated). Some fumes are merely irritants, whereas others can be toxic.
Mists are particles of substances which are carried through the air in droplets (usually of water). They can settle on floors, making them slippery, and reduce visibility by settling on windows and light fittings.
2. Where might they be encountered?
You can encounter fumes and mists in many areas, the most common being:
Remember: fumes can remain in vats, tanks, drums, etc. long after the contents have been removed and additional care must be taken when entering confined or poorly ventilated spaces.
- carbon dioxide at breweries and distilleries (given off during fermentation);
- carbon monoxide in vehicle sheds;
- acetone at food manufacturers;
- benzene at oil installations;
- methanol at distilleries and oil installations;
- ethyl alcohol at distilleries and breweries.
- gases present inside of containers given off by the contents, such as formaldehyde, toluene, benzene, xylene or carbon monoxide. See Gas monitoring equipment.
For handling of fumigated containers see:
3. What damage can they cause?
Fumes and mists generally cause damage after they are inhaled into the respiratory system, attacking the lungs, brain, nervous system and other organs. However, they can pose other dangers by:
- settling on floors, making them slippery;
- reducing visibility by settling on light fittings and windows;
- causing fires if they come into contact with certain types of electrical apparatus;
- bursting into flames or exploding if they are ignited.
4. What can be done to reduce the risks?
As many fumes, and some mists, are not visible, the most important thing is to know when and where they are likely to arise.
Often, notices will be displayed in danger areas on a trader’s premises. If proper ventilation is not provided but you have to work in these areas when mists or fumes are likely to be generated, you must wear respiratory protection.
- Dust masks will not provide protection against fumes and mists.
- Respiratory protection may only be used by officers who have been trained.
If you work in confined spaces, such as on a vessel, hazardous fumes or gases could be present. You must use gas monitoring equipment
to check both the level of atmospheric oxygen and if any hazardous fumes are present.
5. Flammable atmospheres
Flammable gases, vapours and mists are produced or used in many industrial processes. If they are not properly controlled, they can cause serious explosions or fires. Areas where such atmospheres are present are known as hazardous zones and are classified as:
- zone 0 if an explosive gas/air mixture is always present;
- zone 1 if an explosive atmosphere is likely to be produced; and
- zone 2 if an explosive atmosphere is not likely to be produced, but could be for short periods.
The main requirement in these zones is to prevent any chance of the atmosphere being ignited, by excluding all potential ignition sources.
Some of these are obvious, such as matches, lighters and lighted cigarettes, but others are less so. Flammable atmospheres can also be ignited by:
- motor vehicles;
- electrical apparatus (mains or battery-operated);
- sparks from hand tools;
- some types of mobile telephone and radio.
Whenever any type of electrical equipment or hand tool has to be used in a hazardous zone, special precautions will be necessary. You must find out the trader’s safety rules and follow them.
You must use ‘intrinsically safe’ equipment whenever there is a risk that the atmosphere could be flammable.
6. What does ‘intrinsically safe’ mean?
Intrinsically safe equipment is ‘equipment and wiring which is incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a specific hazardous atmospheric mixture in its most easily ignited concentration.’