In homes where there is a high demand for hot water, homeowners often turn up the temperature on their hot water heaters to meet this need, sometimes well beyond the 120 degree Farenheit factory setting considered safe. Temperatures higher than this can cause severe scalding. At highest risk are children and elderly or disabled persons.
In such situations, installing an anti-scald device is an affordable way to protect against this risk.
SOURCE: SHRINER BURNS HOSPITAL