This optical smoke alarm is an entry level smoke alarm at a great price that still conforms to EN14604:2005. Best suited for smouldering fires, they are designed to be used in hallways, bedrooms, and offices - a house should have a combination of optical and ionisation.With a built in test and hush function, the economy optical smoke alarm is an ideal alternative to a mains powered alarm where you cannot easily supply mains power to an area.