Preventing scalding / controlling Legionella

Until recently thermostatic mixing valves (TMVs) were installed as a matter of course in hospitals and care facilities to prevent scalding incidents to patients and residents. However, the Health and Safety Executive’s revised HSG274 part 2 guidelines, Legionnaires’ disease Part 2: The control of legionella bacteria in hot and cold water systems1 state that: ‘The use and fitting of TMVs should be informed by a comparative risk assessment of scalding risk versus the risk of infection from Legionella.’ As a result, there has been marked interest in other technologies to deliver mixed water at the point-of-use. There are three types of technology that offer different levels of anti-scalding safety that are appropriate for use by not just patients, but also by staff and visitors.

The risk of scalding depends on the use and the user. A low level of risk is where there is a habitual user who is familiar with the outlet and the type of mixer, tap, or shower – for example healthcare workers who use a particular basin for regular handwashing. An intermediate level of risk would be present with hospital visitors, who use the public facilities when visiting patients. While such individuals may not be familiar with the facilities, they have no sensory or mobility issues, and are able to use the washbasins safely, especially if there are visual warnings about hot water, and the facilities are easy to use. 

The most serious risk