The FDS series ionization smoke detectors offer a high standard of performance and quickly respond to visible and invisibie combustion products geherated by fire in its incipient stage. They are suitable for a wide range of applications inoffice buildings, hotels, etc. operating principle of these detectors are as follows. Basically. the ionization smoke detector consists of an open sampling chamber (i.e. accessible to ambient air ) , a sealed reference chamber and electroniccircuit for alarm evaluation. Air in both ionization chambers is ionized by small amount of americium 241, abd wutg D,C, voltage applied to the electr odes, aweak electric current flows within the inonization chambers.

When combustion productsener the sampling chamber, thecurrent falls and the sampilng chamber voltage rises, whereby teh reference chamber voltage falls, This disturbance of the balance between the two ionizationchambers is evaluated by means of the electronic circuit as sn alarm signal, which is transmitted to the control panel.