An alarm system comprising: an alarm handset and a cradle for supporting the handset such that the handset is removable therefrom; the handset having: a housing; a detector circuit having means (102, 104) for receiving a preselected signal from a remote transmitter indicative of the detection of radiation, noxious gasses or air pollutants and generating a first detection signal in response thereto; first sensing means for sensing the removal of the handset from the cradle; warning means comprising a light generating means for generating a warning signal, and means for controlling said warning means, in response to receipt of said detection signal, so as to operate the light generating means in a first mode of operation so as to act as a visible warning; alarm means for generating an audible alarm signal; and control means responsive to receipt of said detection signal to activate said alarm means; wherein said control means is further operable to deactivate said alarm means or activate said alarm means to generate a different sound pattern and to activate said warning means in response to the removal of said handset from said cradle after receipt of said detection signal and wherein this comprises operating the light generating means in a second mode of operation so as to act as a torch. an alarm handset and a cradle for supporting the handset such that the handset is removable therefrom; the handset having: a housing; a detector circuit having means (102, 104) for receiving a preselected signal from a remote transmitter indicative of the detection of radiation, noxious gasses or air pollutants and generating a first detection signal in response thereto; first sensing means for sensing the removal of the handset from the cradle; warning means comprising a light generating means for generating a warning signal, and means for controlling said warning means, in response to receipt of said detection signal, so as to operate the light generating means in a first mode of operation so as to act as a visible warning; alarm means for generating an audible alarm signal; and control means responsive to receipt of said detection signal to activate said alarm means; wherein said control means is further operable to deactivate said alarm means or activate said alarm means to generate a different sound pattern and to activate said warning means in response to the removal of said handset from said cradle after receipt of said detection signal and wherein this comprises operating the light generating means in a second mode of operation so as to act as a torch. a housing; a detector circuit having means (102, 104) for receiving a preselected signal from a remote transmitter indicative of the detection of radiation, noxious gasses or air pollutants and generating a first detection signal in response thereto; first sensing means for sensing the removal of the handset from the cradle; warning means comprising a light generating means for generating a warning signal, and means for controlling said warning means, in response to receipt of said detection signal, so as to operate the light generating means in a first mode of operation so as to act as a visible warning; alarm means for generating an audible alarm signal; and control means responsive to receipt of said detection signal to activate said alarm means; wherein said control means is further operable to deactivate said alarm means or activate said alarm means to generate a different sound pattern and to activate said warning means in response to the removal of said handset from said cradle after receipt of said detection signal and wherein this comprises operating the light generating means in a second mode of operation so as to act as a torch.