Visual Alarm Device ("VAD")

In simple terms, when an active alarm condition exists, the visual alarm device is activated and emits a white or red flashing light. The flash rate of a VAD is between 0.5 Hz and 2 Hz of between pulses with a light intensity of not less than 1 candela (cd) and not more than 500 candela.

A Visual Alarm Device Class (or VAD Class) defines the standardised physical mounting orientation, maximum installation height, and three-dimensional light coverage envelope for a visual warning strobe certified under fire safety performance standards.

Class C: Ceiling-Mounted Devices (C-ꭓ-𝐲)

Class C devices are certified for ceiling installation and project a downward-pointing, cylindrical light coverage pattern onto the floor area below. They are identified using the code format (C-ꭓ-𝐲), where;

• ꭓ (Maximum Mounting Height): The maximum permissible installation height in metres (standardised between 2.5 m and 10 m) above finished floor level.
• 𝐲 (Coverage Diameter): The diameter in metres of the circular illumination footprint projected onto the ground when the device is mounted at height x.
• Example (C-3-12): A ceiling strobe installed at a maximum height of 3 metres that provides compliant illumination across a cylindrical footprint with a 12-metre diameter (which accommodates a square area measuring 8.49m × 8.49m inscribed within the circular beam).

Class W: Wall-Mounted Devices (W-ꭓ-𝐲)

Class W devices are photometrically certified for vertical wall mounting and project a rectangular box-shaped (cuboid) visual volume outwards and downwards across a floor region. They are identified using the code format W-ꭓ-𝐲:

• ꭓ (Maximum Mounting Height): The maximum installation height in metres on the wall (with a baseline specification starting at 2.4m).
• 𝐲 (Coverage Width and Depth): The side lengths in metres of the square coverage area projected across the floor in front of the wall.
• Example (W2.6-6): A wall strobe installed at up to 2.4 metres above floor level that illuminates a rectangular coverage volume measuring 2.4 metres high, 6 metres wide, and 6 metres deep (2.4m × 6m × 6m).

Class O: Open-Category Devices

Class O devices accommodate non-standard architectural environments where fixed cylindrical or cuboid coverage shapes cannot effectively cover the space:

• Flexible Spatial Geometry: Allows manufacturers to specify non-standard coverage shapes, custom mounting orientations, or specialised light distribution patterns outside the rigid limits of Class C or Class W.
• Manufacturer Data: The precise coverage volume, mounting geometry, light distribution pattern, and maximum operating heights must be explicitly declared by the manufacturer based on independent laboratory testing.