Optical smoke alarms, also known as photoelectric detectors, have a high sensitivity to large particles in the air. They are slightly quicker at detecting slow-smouldering fires that produce a lot of smoke (such as fire from soft furnishings). They are suitable for living rooms and sleeping areas and are used near kitchens as they are less prone to false alarms.
Ionisation smoke alarms use a small amount of radioactive material in the sensor chamber to detect fires, as such they are being discontinued. Safelincs encourages customers to purchase optical smoke alarms instead.
See also heat alarms for the most suitable protection in a kitchen.
Read more about how different smoke alarms work.