The most common forms of warning device are audible. In order to comply, such devices must emit a sound level and frequency within the parameters set by British Standards.
To comply with the Equality Act 2010 and other statutory documents such as Building Regulations, there is increasing use of additional visual indication in premises to alert persons with hearing impairment. Other types of warning device include vibrating pads and fire paging systems which are also designed for the hearing impaired. Standalone beacons or combined sounder and beacon units are widely installed in premises where there is a high ambient noise level. Voice evacuation is becoming increasingly popular in buildings used by the general public where the fire alarm tone may not be recognised and there is the potential for persons to otherwise remain in a building when the fire alarm has activated.