Introduction
1. The most
important route by which hazardous agents such as chemicals, biological agents,
etc enter our bodies is through inhalation. The best way to protect
workers from inhaling such hazardous agents is to reduce or prevent
contamination of the air they breathe through the use of engineering control
measures such as enclosures, local exhaust ventilation systems and substitution
of to a lower risk agent. Where such measures are not feasible or cannot
be implemented immediately or are inadequate to control the inhalation hazard,
then respiratory protection has to be used. Respiratory protection may
also have to be used in maintenance operations or during emergencies.
Aim
2. To
outline the requirements for use of respirators in laboratory based research and
teaching activities in NUS.
What should you use
a respirator?
3. There are two
main indicators for respirator use:
a. When
exposed to hazardous air contaminants in concentrations which exceed the
permissible exposure limits/levels – this is determined via a risk assessment (for
information on risk assessment, refer to the NUS risk assessment system)
b. When
in an oxygen deficient environment (<19%) e.g. in a confined space such as a
storage tank or manhole
c. If
you are not sure if your research or teaching activities require risk
assessment, please contact your safety officer or OSHE.
What do ensure your
respiratory is effective?
4. If respirators
are used, they should be used properly so as to ensure effective protection.
Otherwise they can give a false sense of security and in fact be a danger to the
user.
5. For
respirators to be effective, they must:
a. Be
of the correct type for the situation or hazard
b. Fit
the persons using them
c. Be
worn all the time in the hazardous environment
d. Be
properly maintained in good working condition
What are the types
of respirator available?
6. There is no all
purpose respirator. It is very important to select the correct type of
respirator for the particular hazard or situation. Basically, there are
two types of respirators: air-supplied and air-purifying.
7. Air-supplied
respirators provide a separate supply of air e.g., air-line respirators and
self-contained breathing apparatus (SCBA). These respirators must be used
when in an oxygen deficient environment or when the levels of the contaminants
are at very high concentrations beyond the protective limits of most
air-purifying respirators. Examples of such situations are maintenance
operations or emergencies e.g. fire-fighting, rescue and accidental leakage.
8. Air-purifying
respirators work by filtering or absorbing air contaminants as they pass through
the respirator filter or cartridge. There are filters for particulates
e.g. dust, mist and fume and cartridges for aerosols, vapours and gases.
Some of the cartridges are specific for certain types of gases or vapours.
Sometimes, a combination of a toxic dust filter and an organic solvent cartridge
is required e.g. a worker exposed to both pesticide dust and solvent
vapour. The respirators also come in various types of facepieces e.g.
full-face mask or half mask. Full-face mask respirators have the advantage
of eye protection and a higher protection level but are heavier and bulkier.
There are also disposable respirators which have the advantage of being lighter
and being maintenance free. However, these may not be available in
different sizes.
How should you wear
your respirator properly?
9. There must be a
good seal between the edges of the respirator and your face. Otherwise,
the air contaminants would leak in through the edges of the respirator.
The following may contribute to poor fit: wrong size of respirator, wrong
method of wearing respirator, wrong positioning of facepiece or straps, straps
too loose, beard, facial deformities, defective respirator.
10. To ensure
proper fit:
a.
Select the correct size/type of respirator.
b.
Put on the respirator according to the
manufacturer's instruction, adjusting the straps and facepiece to obtain the
test fit.
c.
Carry out a fit test at a time of issue of
respirator. (Fit test: This is based on the ability to taste an
aerosol of a substance like saccharin with the respirator worn. With a
proper fit, your should not be able to taste it) and
d.
Carry out fit checks each time the
respirator is used. (Fit checks: With the respirator worn, cover the
filter or cartridge with the palm of your hands. Breathe in and hold your
breath. The facepiece should collapse slightly and remain so, if there is
no obvious leak).
Consistent Usage
11. The protection
factor is reduced each time the respirator is removed in the presence of
contaminanted air. They should be worn all the time while in a contaminanted
environment.
How should you
maintain your respirator?
12. The cartridges
or filters of non-disposable respirators must be regularly changed to ensure
continued protection. Particulate filters should be changed once they are
clogged up resulting in increased breathing resistance. Gas and vapour
cartridges must be changed once they are saturated and can no longer absorb any
more of the contaminants. This would be indicated by a “breakthrough” of
the chemical into the respirator e.g. smell or irritation by the chemical.
The higher the concentration, the more frequent the change. Once there is
a breakthrough of the contaminant, the worker must leave the area and change the
cartridge immediately. There must be good warning properties of the
contaminant in order that a breakthrough can be detected. Otherwise
air-supplied respirators are indicated.
What training is
required for use of respirators?
13. All personnel
required to use respirators at work need to be adequately trained in its use.
The training should cover the areas highlighted within this document, and also
specific to the respirator being used along the course of their work.
Why do I need to do
a Medical Fitness test?
14. Most workers
should have no problems breathing through the respirators and working. A
few workers with poor lung or heart function may have difficulty breathing
through the respirators. Workers with poor effort tolerance or unstable
angina may have difficulty doing strenuous exercise and carrying the heavy
air-supplied respirators. Where indicated, lung function tests and stress
ECG can be carried out. The conduct of medical fitness examinations are to be
done by a Designated Factory Doctor or an Occupational Health Physician. This
should be done at the University Health and Wellness Centre. NUS would fund for
respiratory related medical tests
(please refer to NUS Occupational Health Programme
https://wws.nus.edu.sg/osh/programme/ohp/index.htm)
Laboratory
Respiratory Protection Programme
15. Departments or
PIs that require their personnel to use respirators for laboratory based
research and teaching activities should implement a self-regulatory and
comprehensive respiratory protection programme. This should include the
following:
a. Risk
assessment of laboratory based activities to determine exposure potential.
b. Engineering
control to reduce the hazard where practicable
c. Selection
and provision of suitable respirators if engineering controls are unable to
reduce exposure to acceptable levels
d. Medical
examinations for fitness of staff and students (to be done at UHWC)
e. Training
in use and care of respirators
f. Supervision
to ensure proper fit and consistent usage
g. Proper
maintenance of respirators
h.
Regular environmental monitoring of
exposure levels to ensure effectiveness of respirators
Conclusion
16. A comprehensive
respiratory programme is required where there is risk of inhalational hazards
(such as chemical and biological hazards). A respirator may be used routinely or
during emergencies. To ensure effective use of respirators, personnel need to be
fit-tested, medically fit to wear respirators and trained in its use.
Reviewed by:
Mr Saravanan G
Occupational Safety and Health Manager, OSHE
Prepared by:
Dr Gregory Chan
Senior Occupational Health Advisor, OSHE
Reference:
Singapore Standard CP 74: 1998, Code of Practice for Selection, use and
maintenance of respiratory protective devices
