Other Risk Systems
Guidance
There are a number of other systems (which
produce aerosols) which may pose a risk of
exposure to legionella. These include:
* Spa and whirlpool baths - a spa is a bath
or a small pool where warm water is constantly
recirculated, often through high-velocity
jets or with the injection of air to agitate
the water. The water is not changed after
each use; instead, it is filtered and chemically-treated.
The water temperature is normally greater
than 30C and the deliberate agitation creates
a spray or aerosol above the surface of the
water. They therefore present a foreseeable
risk of exposure to legionella. Careful attention
to design, maintenance and cleaning of equipment
such as filters, and regular water treatment
to prevent/control the risk from legionella
is required. Spa baths can be a risk even
when not being used by bathers, for example
when being run for display purposes. Whirlpool
baths (baths fitted with high velocity water
jets and/or air injection but without water
recirculation) do not present the same risk
as spas because the water is discharged after
each use.
* Humidifiers and air-washers - atomising
humidifiers and spray-type air-washers may
use water from reservoirs or tanks where the
water temperature exceeds 20C. Unless they
are regularly cleaned and maintained, they
can become heavily contaminated, especially
in industrial environments. The risk can be
prevented by using humidifiers which do not
create a spray, i.e. steam humidifiers. 'Portable'
or 'room' humidifiers of the type that have
a water supply that is sprayed or atomised
into the room are not recommended for use
in NHS premises.
The actions that need to be taken with regard
to the systems outlined and for some other
recognised risk systems are detailed. In general,
these systems and any others found to present
a risk should be maintained in a clean state,
will often require regular disinfection and
should be monitored on a regular basis where
appropriate. There is also a duty to carry
out a risk assessment and to maintain records
of all maintenance that is carried out together
with monitoring results. Great care needs
to be taken during installation and commissioning
to ensure that cross-connections do not occur
between different water systems, e.g. fire
mains and cold water systems.
Protection of personnel
Maintenance, cleaning, testing and operating
procedures should all be designed to control
the risks to staff and others who may be affected.
Cooling towers and evaporative condensers
should be treated as described in the section
on cleaning and disinfection and, in particular,
the requirement for pre-cleaning disinfection
should be observed. This will only have a
transient effect on legionella, but it will
reduce the chance of engineering staff being
exposed while working on the tower. Where
possible, cleaning methods which create spray
(for example, high-pressure water jetting)
should be avoided. If this is not possible,
the operation should be carried out when nearby
buildings are unoccupied or, in the case of
permanently occupied buildings, windows should
be closed and air inlets temporarily blanked
off.
As systems requiring cleaning may have been
contaminated, the operator and others closely
involved in the work should wear suitable
respiratory protective equipment. This can
be a powered filter and hood, European Class
TH3 (assigned protection factor of 40) or
a powered assisted filter and close-fitting
full-face mask, TM3 (assigned protection factor
of 40). It should be borne in mind that the
filter on these systems is liable to get wet,
and so resistance to air can increase, causing
discomfort to the operator.
Alternatively, a hood or full-face mask fed
with breathing quality compressed air may
be used. The preferred equipment is a full-faced
mask close-fitted airline mask, with a positive
pressure demand valve, under a hood or helmet
protecting the rest of the head. The air supply
should come from an oil-free compressor drawing
air through a filter from a location well
up-wind of any jetting operation or using
cylinder supplies of compressed air. Further
information on respiratory protective equipment
can be obtained from The Selection, Use and
Maintenance of Respiratory Protective Equipment:
a practical Guide.
Use of treatment chemicals
Many water treatment chemicals, including
chlorine-containing chemicals and solutions,
are often hazardous and need to be used with
care. The COSHH assessment and many manufacturers'
recommendations need to be followed to ensure
that the chemicals do not endanger the users
or other people. Proprietary biocides, other
than those permitted by the Water Regulations,
should never be used in drinking water or
in hot and cold water services and should
not be discharged into sewers, storm water
drains or natural watercourses without prior
permission of the relevant water company (or
authority in Scotland). Contact may also need
to be made with the Environment Agency in
England and Wales and the Scottish Environment
Protection Agency in Scotland, who may have
responsibility for direct discharges into
watercourses. Water treatment chemicals are
not recommended for use in humidifiers and
airwashes when buildings are occupied.The
handling of these water treatment chemicals
should be carried out by trained operators
under the direction of people who are suitably
qualified, experienced and trained.
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