Legionnaires' Disease: Technical Guide Part 3 - Control of Legionella Bacteria in Other Risk Systems
This guide has been prepared to assist duty holders, including employers, building managers, and others responsible for health and safety, in fulfilling their legal obligations. These obligations include identifying and assessing risk sources, preparing a plan to prevent or control the risk, implementing, managing, and monitoring the measures, keeping records related to the measures, and appointing a responsible manager.
The guide provides practical advice on the legal requirements of relevant legislation such as the Health and Safety at Work Act 1974, the Control of Substances Hazardous to Health Regulations 2002, and the Management of Health and Safety at Work Regulations 1999.
Introduction
Practical advice on legal requirements regarding the risk of exposure to Legionella bacteria is contained in the document Legionnaires’ disease: The control of legionella bacteria in water systems. Approved Code of Practice and guidance on regulations (L8). This guide directs duty holders on assessing and controlling legionella risk in risk systems other than evaporative cooling systems or hot and cold water systems.
What Are Other Risk Systems?
Besides evaporative cooling and hot/cold water systems, other systems that can generate aerosols and pose a risk of legionella exposure include (this list is not exhaustive):
- Ultrasonic humidifiers/misters
- Misting devices used to humidify vegetables, meat, and other food products
- Spray humidifiers
- Air washers, wet scrubbers, particulate and gas scrubbers
- Water softeners
- Emergency showers, eye baths, and face wash taps
- Sprinkler and hose reel systems
- Spa pools
- Jacuzzi baths
- Gardening misting systems
- Automatic vehicle washing systems (cars, buses, trucks, railway vehicles)
- High-powered dental equipment
- Fountains and decorative water features displayed for sale
- Reusable nebulizers used for respiratory therapy
- Industrial wastewater treatment plants
- Irrigation systems
- Fire, dust, and odor suppression systems
- Paint spray preparation equipment
- Tunnel pasteurizers and similar equipment
Most of these systems operate at or above ambient temperature, and some may experience seasonal thermal gain. For example, outdoor irrigation systems may use water within the temperature range suitable for legionella bacteria growth. All these systems can produce water droplets (aerosols) during operation, and some, such as dental equipment and nebulizers, can deliver these aerosols directly to the respiratory area.
The highest risk systems are spa pools, and the Management of spa pools: Controlling the risks of infection HSE/PHE guide should be followed. Jacuzzi baths are not considered high risk if the water is drained immediately after each use and the source water is safe.
Risk Identification and Control
As with any foreseeable risk system, a risk assessment should be conducted, additional measures taken if necessary, and all maintenance and monitoring records kept. These systems generally use mains water and are therefore subject to the 1999 Water Supply (Water Fitting) Regulations and the 2001 Water Supply (Water Quality) Regulations.
The following factors should be considered during risk assessment:
- Likelihood of legionella contamination of the water source
- Potential for microorganism proliferation
- Potential for aerosol formation
- Presence and susceptibility of persons exposed to aerosols
If the risk assessment concludes that legionella exposure risk is insignificant and well managed, no further action is required, but the assessment should be reviewed regularly. If risk exists:
- Consider whether the system can be replaced with a dry system.
- If impractical, prepare and implement a written plan to prevent or control the risk.
- Monitor control measures and record results.
- Record significant findings of the risk assessment and specify when it will be reviewed.
- Update the written plan if the risk changes.
- Ensure competence of persons responsible for risk control and clarify duties, responsibilities, and reporting lines.
If there is insufficient information or expertise during risk assessment, expert assistance should be sought.
Recommended Inspection Frequency Checklist for Other Risk Systems
| System/Service | Task | Frequency |
|---|---|---|
| Ultrasonic humidifiers/misters and water misting systems | Check effectiveness of UV lamps and clean filters | Every six months or per manufacturer instructions |
| Operation of automatic drain of residual water | When machine is switched off | |
| Cleaning and disinfection of all wet parts | According to risk assessment | |
| Legionella sampling | According to risk assessment | |
| Spray humidifiers | Cleaning, disinfection, and descaling | Every six months |
| Non-chemical water treatment control | Weekly | |
| Air washers, wet scrubbers | Cleaning, disinfection, and water tank maintenance | According to risk assessment |
| Water softeners | Cleaning and disinfection of resin and salt tanks | Per manufacturer recommendation |
| Emergency showers, eye baths, face wash taps | Flushing and rinsing water | According to risk assessment, at least every six months |
| Water tank inspection | Monthly | |
| Cleaning of shower heads, nozzles, filters, and water tanks | Every three months or per risk assessment | |
| Sprinkler and hose reels | Control of aerosol exposure risk during tests | Per instructions |
| Spa pools | Follow HSE/PHE guidance | - |
| Jacuzzi baths | Cleaning of air ducts, jets, and rinsing | According to risk assessment |
| Gardening misting systems | Cleaning, disinfection, and descaling of distribution pipes, spray heads, and tanks | Every three months or per risk assessment |
| Dental equipment | Draining, cleaning, rinsing, and disinfection of all system components | Twice daily (usually at start and end of work) |
| Cleaning and rinsing of storage bottles | Daily | |
| Microbiological testing | According to risk assessment | |
| Vehicle washing systems | Cleaning of filtration systems, collection, and treatment tanks | According to risk assessment |
| Legionella sampling | Initially and then every three months or per risk assessment | |
| Fountains and water features | Cleaning, disinfection, and descaling of pools, spray heads, and tanks | According to risk assessment |
| Industrial process water systems | Risk assessment and preparation of control plan | According to risk assessment |
References
- Legionnaires’ disease: The control of legionella bacteria in water systems. Approved Code of Practice L8 (Fourth edition), HSE Books 2013, www.hse.gov.uk/pubns/books/l8.htm
- Management of spa pools: Controlling the risks of infection, HPA/HSE 2006, www.hse.gov.uk/legionnaires/spa-pools.htm
- Water Supply (Water Fitting) Regulations 1999, SI 1148/1999, The Stationery Office
- The Water Supply (Water Quality) Regulations 2001, SI 3911/2001, The Stationery Office
- Decontamination Health Technical Memorandum 01-05: Decontamination in primary care dental practices, 2013, Department of Health, www.gov.uk
Acknowledgements
The cover photo is used with permission from Public Health England. HSE thanks the following organizations for their contributions to the preparation of this technical guide:
- Legionella Control Association (Howard Barnes, Robert McLeod-Smith)
- British Association for Chemical Specialities (Tim Parkinson, Geoff Walker, John Smith)
- Water Management Society (John Lindeman, Alan Elsworth, Mike Hunter, Graham Thompson, Giles Green, Alan Greaves, Susanne Lee)
- Dr. Tom Makin
Additional Information
For information on health and safety or to report inconsistencies in the guide, visit www.hse.gov.uk. HSE guides can be viewed online and paid publications ordered. Legislation is available free at www.legislation.gov.uk.
This guide was first published in 11/13 and is Crown copyright. For reuse, visit www.hse.gov.uk/copyright.htm.