Legionella bacteria are water-loving soil bacteria that are found naturally in the environment. The bacteria are hazardous when inhaled into the lungs, as they cause Legionnaires Disease (Legionellosis).
Legionella can occur when water systems in a building become contaminated with the bacteria (which breed in warm conditions) and then the contaminated water is sprayed to create a mist (with living bacteria within the droplets).
The risk of Legionella in church buildings and manses is very low and largely depends on how water is supplied to your building, how the water is stored and how the water is heated and distributed to your taps, toilets and, in some cases, showers and air conditioning systems.
HSE has updated their guidance, stating that even water supplied directly from the mains water supply may pose a small risk of transmitting legionella.