Hi Smoke alarms come in various guises these days,whilst not a total list the following may help. Firstly your post says "Smoke" alarm.As such two main types are easy to obtain Optical or Ionisation. Mainly people tend to adopt the Optical sensors but both detect the presence of smoke in the case of fire. These can be a pain in a kitchen and normally a temperature rise device or Heat detector is employed.
Next is the power supply for the device. Mains powered units are preferred and most have a built in rechargeable battery in case of mains failure. Failing this battery only devices are available from a simple 9v PP3 to a
5yr lithium battery.
If fitting more than one device a linked system is useful ;not to be confused with a fire alarm system these devices have linked cabling and each device will repeat the activation of any devices on the link.
Like everything these days you get what you pay for so the more the sensor has to offer the dearer it will be.
Google smoke detectors for 1000's of options and pictures but check the Spec' before buying.
HTH CJ
Anyone familiar with these? I need to replace mine and I'm hearing that there are at least two types. If I'm going to buy something I might as well go for something that will cover all evetualities - not just burnt toast.