Other Risk Systems
||There are a number of other systems (which produce aerosols) which may pose a risk of exposure to legionella. These include:
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.