In brief
Legionella bacteria live in water, multiply between 20–45 °C, and can cause Legionnaires' disease when water droplets from a cooling tower, shower head or rarely used tap are inhaled. The essence of control is temperature control, preventing water from stagnating, regular cleaning and records showing these. The Biological Agents Regulation classifies Legionella in Group 2; the risk should be treated as a separate heading in the workplace risk assessment.
Where does Legionella risk arise at work?
Legionella is a bacterium found in low numbers in natural waters. The problem starts when the bacterium multiplies in building and plant water systems: lukewarm water, stagnation, sediment, scale and biofilm give it a suitable environment. The disease is not caught by drinking the water but by inhaling water droplets (aerosols) containing the bacterium. So when Legionella risk in the workplace is considered, the question should not be "is our water clean?" but "which point of our system is lukewarm, stagnant and producing aerosols?"
| Source | Why does it create a risk? | Priority measure |
|---|---|---|
| Cooling towers and evaporative condensers | Lukewarm water, large surface, water droplets blown out by the fan | Water treatment programme, drift eliminator, regular cleaning |
| Hot water tanks and calorifiers | Sediment at the bottom of the tank, insufficient temperature | Monitoring storage temperature, draining sediment |
| Changing room showers | Scale and biofilm in the shower head, aerosols | Head cleaning, flushing after long shutdowns |
| Eyewashes and emergency showers | Water unused for weeks, warming up | Regular flushing and records |
| Rarely used taps and dead legs | Stagnant water | Weekly flushing or removal of dead legs |
| Cold water tanks | Stagnant water warming up and becoming contaminated | Temperature control, periodic cleaning |
Cooling towers used in processes such as plastic injection moulding, metalworking and textiles in the OIZs (organised industrial zones) of Bursa and the surrounding provinces, the crowded changing rooms of shift-working factories and the region's thermal facilities are the on-site equivalents of this table.
Legionnaires' disease: who is at risk?
Legionnaires' disease is a severe pneumonia caused by Legionella. The same bacterium can also cause Pontiac fever, which takes a milder, flu-like course. The disease is generally not transmitted from person to person; the source is a contaminated water system. Older age, smoking, chronic lung, heart or kidney disease, diabetes and immunosuppressive treatments increase the risk.
The Regulation on the Prevention of Risks from Exposure to Biological Agents classifies Legionella pneumophila in Group 2: agents that can cause disease in humans, are unlikely to spread to the community and for which effective prophylaxis or treatment is usually available. Under the regulation, every case of disease or death resulting from occupational exposure to biological agents is reported to the Ministry (Art. 16/10). For risk groups and record-keeping obligations, see our article on biological agents and risk groups.
Cooling tower maintenance technicians, plumbers working on water systems and cleaning teams are the groups most exposed. The workplace physician assesses symptoms of febrile respiratory infection in these workers for their relationship with work. A disease linked to work is treated as a suspected occupational disease; for the process, see our article on occupational disease diagnosis and notification.
Hot water temperature and Legionella: control values
Turkish OHS legislation does not set numerical temperature values for workplace water systems. In practice, international guidance is used. The Legionella guidance of HSE, the UK health and safety authority, gives the following values:
- The bacterium multiplies between 20–45 °C where nutrients are available; it is dormant below 20 °C and cannot survive above 60 °C.
- Hot water storage tanks are kept at 60 °C or above.
- Hot water is distributed at 50 °C or above.
- Cold water is stored and distributed below 20 °C.
- The outlets nearest to and furthest from the tank are chosen as "sentinel taps", and the temperature is measured at these points.
Showers, eyewashes and rarely used outlets
Showers are the most frequently overlooked source at workplaces, because they produce aerosols and, depending on the shift pattern, are left unused for long periods. The HSE guidance recommends two simple rules: rarely used outlets (including shower heads and taps) are flushed at least once a week, and shower heads and hoses are cleaned and descaled at least every three months.
A workable arrangement on site can be set up as follows:
- Draw up an inventory: Mark all showers, eyewashes, emergency showers and rarely used taps on a floor plan.
- Prepare a flushing schedule: Assign a responsible person and day for each outlet. During flushing, open the water slowly to reduce aerosols and keep the head away from face height.
- Flush after long shutdowns: After a public holiday or maintenance shutdown, all showers and taps are flushed before the plant reopens. For pre-holiday preparation, see our article on shutting down the plant before a long holiday.
- Do not forget eyewashes: Eyewashes in chemical areas are flushed regularly and recorded, both for functionality and for water quality.
- Remove dead legs: If an unused shower or basin has been removed, also cap its supply pipe at a point close to the main line.
Cooling tower maintenance
Cooling towers can carry the risk beyond the work area because of the water droplets blown out by the fan. Keep the following elements in writing as a programme for cooling tower maintenance:
- Water treatment: Dosing of biocide, corrosion and scale inhibitor is done according to the supplier's written programme; dosage and test results are recorded.
- Drift eliminator: Check that the drift eliminators, which reduce the droplets emitted by the tower, are in place, intact and clean.
- Cleaning and disinfection: Sludge and sediment in the pond are cleaned regularly; after a long shutdown the tower is cleaned before being brought back into service.
- Location: The proximity of the tower outlet to ventilation air intakes, windows and pedestrian routes is addressed in the risk assessment.
- Sampling: We plan Legionella analysis of water samples with authorised laboratories; the results and measures taken are entered in the same file.
The technician working on the tower is the person closest to the aerosol. Suitable respiratory protection is used during cleaning, and fans and pumps are de-energised by locking and tagging them out. For the lockout steps, see our article on LOTO lockout and tagout, and for choosing respiratory protection, our article on PPE selection.
Water tank cleaning
Cold water tanks can warm up on sunny roofs or in hot boiler rooms. The HSE guidance recommends checking the cold water tank temperature at least every six months and cleaning the tank periodically.
Water tank cleaning, however, is an OHS task in its own right. Cleaning done by entering the tank is often confined space work: it requires an entry permit, atmospheric testing, ventilation, a standby person outside and a rescue plan. Chlorine-based products used for disinfection also create a chemical risk; follow the PPE and mixing warnings in the safety data sheet. For preparation, see our article on working in confined spaces. If you use an outside contractor, request the same documents for the contractor's workers too.
Record-keeping and entering it in the risk assessment
If Legionella management does not show on paper, it counts as not done in an inspection and after a case. The following record-keeping arrangement can be adapted from a small factory to a large plant:
| Record | Content | Example frequency |
|---|---|---|
| Water system schematic | Tanks, calorifiers, tower, showers, eyewashes, dead legs | Updated on change |
| Temperature form | Calorifier outlet, temperature at sentinel taps | According to the plant's programme, based on the HSE recommendation |
| Flushing record | Outlet, date, person flushing | Weekly for rarely used outlets |
| Shower head maintenance | Heads cleaned and scale condition | At least every three months |
| Tower programme | Dosing, testing, cleaning, sample results | According to the supplier's programme |
| Corrective action | Deviation, measure taken, close-out date | For each deviation |
Art. 10 of Law No. 6331 on Occupational Health and Safety requires the employer to carry out a risk assessment and to have the necessary checks, measurements and investigations carried out. Legionella should appear in this assessment under the water systems heading, with a separate line for each source. The biological agents regulation also requires exposure to be prevented and, where this is not technically possible, to be minimised (Art. 8).
At Bursa Sistemer OSGB we assess your water systems source by source in the risk assessment and monitor workers in risk groups as part of workplace physician services; we plan water samples and the necessary tests with authorised laboratories and healthcare institutions. For additional risks in accommodation facilities, see our article on OHS in hotels.
Frequently Asked Questions
At what temperature does Legionella multiply?
According to the HSE guidance, the bacterium multiplies between 20–45 °C where nutrients are available; it is dormant below 20 °C and cannot survive above 60 °C. Hot water is therefore stored at 60 °C and above and distributed at 50 °C and above, and cold water is kept below 20 °C.
Is Legionella testing mandatory at the workplace?
OHS legislation does not set a general Legionella testing frequency for workplaces. The need for and frequency of sampling are determined by the risk assessment of your water systems; regular sampling is good practice at plants with cooling towers. Have the analysis done by an authorised laboratory.
Is Legionnaires' disease transmitted from person to person?
Generally not. The source is inhaling water droplets containing the bacterium. So when a case is suspected, the priority is to examine the water system and bring the source under control rather than to separate workers.
How often should shower heads be cleaned?
The HSE guidance recommends cleaning and descaling shower heads and hoses at least every three months, and flushing rarely used showers at least once a week. After long holidays and maintenance shutdowns, flush all showers before the plant reopens.
A physician assigned for the time your hazard class requires: pre-employment and periodic examinations, fitness-for-work reports and health surveillance.
Bursa SİSTEMER OSGB Technical Team — written from the field experience of our OHS specialists and workplace physicians. Legal information is valid as of the publication/update date; contact us for an assessment specific to your business.