Respirators and breathing apparatus
It is not possible to set out precise
requirements for every industrial situation where there is an inhalation
hazard because the factors that have to be considered vary from one
workplace to another. Both the user and the supplier should be satisfied
that the equipment selected is adequate for the conditions. If in doubt,
you should seek technical advice from your equipment supplier, or your
local branch of the Occupational Safety and Health Service of the Department
of Labour (OSH).
Respirators protect against the following hazards:
Respirator protection is required for different categories of dust:
These may cause discomfort (i.e. cough or phlegm) or minor irritation
of the nose and lungs but are normally not toxic and do not permanently
damage the lungs. They pass out of the body or remain in the lungs
without poisoning the system. Examples are calcium carbonate (limestone
dust), starch and sucrose.
Respirable particles of these dusts remain in the lungs where they
may damage the tissue. For example, asbestos, crystalline silica (quartz
dust) and coal dust.
Chemically active particulates that cause immediate discomfort, irritating
or inflaming the airways to the lungs. Examples are acid or alkaline
mists and cement dust.
Dusts that produce flu-like symptoms and fever, sometimes several
hours after exposure. For example, fumes evolved from welding zinc
These pass from the lungs into the blood and may poison the whole
body. For example, lead, arsenic and powdered organophosphate pesticides.
Particulates in low concentration that may cause an allergic reaction.
An example is mould.
- Mists and aerosols:
These are fine droplets of liquid dispersed in the air and may contain
particles of dissolved substances. Mists are produced by condensation
of a vapour or by atomisation of a liquid. Examples are paint spray
and chromic acid mist from an electroplating bath.
- Metallic fumes:
These are fine particles of metal, produced by condensation of the
vapour, given off by a metal when it is subjected to high temperatures,
for example, during welding and smelting. NOTE: Inhaled particles
deposited in the mucus in the respiratory airways will enter the body
- Gaseous or vapour contaminants:
There are three categories of gasses and vapours for which different
types of respiratory protection is required:
- Acid gases, e.g. hydrogen chloride and sulphur dioxide.
- Alkaline gases, e.g. ammonia and diethylamine.
- Organic vapours, e.g. solvents.
- Lack of oxygen and confined spaces:
Before entry into a confined space, it is essential to carry out a
full assessment of the likely contaminants and possibility of oxygen
deficiency. A decision on the appropriate type of respiratory equipment
and other safety factors will then need to be made. For further information,
see the booklet 'Safety in Confined Spaces' available from your local
OSH branch office.
- Criteria for selecting a respirator:
Three main factors need to be considered when selecting a suitable
respirator for a particular situation, you should seek expert advice
from the equipment supplier, your OSH branch office or other authority
on occupational hygiene
- Medical aspects of wearing a respirator:
There are some medical factors that may preclude or limit the use
- People with impaired lung function may experience difficulty
- An asthma attack may be made worse or induced in susceptible
- People with circulatory disease such as heart disease and anaemia
may be adversely affected.
- People prone to epilepsy should be aware of the special dangers
of wearing a respirator should a seizure occur.
- The wearing of contact lenses or spectacles may restrict the
type of respirator that can be worn.
- Psychological factors such as claustrophobia may preclude the
wearing of respirators.
- Facial characteristics such as prominent cheekbones, deep skin
creases, lack of nose bridge, etc. may lead to respirator facepiece
Selection of respirator
PAPR = powered air purifying repirator
SCBA = self-contained breathing apparatus
For further information refer to 'A
Guide to Respirators and Breathing Apparatus' published by the Occupational
Safety and Health Service of the Department of Labour, Wellington.