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How to check illumination coverage for CHQ-WSB2 and YBO-BSB2 visual alarm devices

Both the CHQ-WSB2 and the YBO-BSB2 are EN 54-23 Category 'O' devices, so take their coverage from the volumetric diagram in AP132 or AP133, not from a spacing rule.

Direct answer

Both the CHQ-WSB2 and the YBO-BSB2 are EN 54-23 Category 'O' visual alarm devices. Category O means the manufacturer declares a coverage volume and a volumetric shape rather than a C-x-y ceiling diameter or a W-x-y room width, so their coverage cannot be reduced to a spacing rule or a floor-area formula. To check coverage, confirm the exact ordering code and LED colour, then read the light output volumetric coverage diagram from Application Note 132 (CHQ-WSB2) or Application Note 133 (YBO-BSB2), and confirm the flash rate and any control panel setting that affects it. The two product families are not interchangeable.

Applies to

  • Products / Models: CHQ-WSB2/WL, CHQ-WSB2/RL, CHQ-WSB2(WHT)/WL, CHQ-WSB2(WHT)/RL (wall sounder beacon); YBO-BSB2/WL, YBO-BSB2/RL, YBO-BSB2(WHT)/WL, YBO-BSB2(WHT)/RL, YBO-BSB2(BLK)/WL, YBO-BSB2(BLK)/RL (base sounder beacon). HFP and SIL variants share the same EN 54-23 category; check the application note for the matching model number.
  • Firmware / Version: Not applicable. Flash rate (0.5 Hz or 1 Hz) is set at the control panel and requires panel compatibility.
  • Region: UK / Europe
  • Standards: EN 54-23 — both families are Category 'O'. The sounder element is covered by EN 54-3; where an isolator base is used, EN 54-17 also applies to that base.

CHQ-WSB2 wall sounder beacon variants

  • All CHQ-WSB2 variants are EN 54-23 Category 'O' (open class). Note that "wall sounder beacon" describes where the device is mounted, not its EN 54-23 category — the CHQ-WSB2 is not W rated, so the W-category cuboid rule does not apply to it.
  • Hochiki publishes the O rating as a light output volumetric coverage diagram in Application Note 132, with the device oriented so that the front of the unit faces along the X-axis of the diagram. Read the coverage volume and the shape from that document for your exact variant and LED colour; the published volume differs between the white and red LED versions.
  • The published EN 54-23 coverage is declared at a 0.5 Hz flash rate. These devices can also be set to 1 Hz where the control panel supports it, and the published coverage does not apply at that setting. Confirm the flash rate configured at the panel before applying any coverage figure.
  • Do not convert the volumetric coverage into a single floor area or diameter. There is no published cylinder dimension or cross-section formula for this device.

YBO-BSB2 base sounder beacon variants

  • All YBO-BSB2 variants are EN 54-23 Category 'O' (open class). For a category O device the manufacturer declares a coverage volume and the volumetric shape that goes with it; there is no ceiling diameter or floor-area formula to apply, and none is published.
  • Hochiki publishes the O rating as a light output volumetric coverage diagram in Application Note 133. Take the volume, the shape and the mounting orientation from that document for the exact variant and LED colour — the published light volume differs substantially between the white and red LED versions.
  • The published EN 54-23 coverage is declared at a 0.5 Hz flash rate. These devices can also be set to 1 Hz where the control panel supports it, and the published coverage does not apply at that setting. Confirm the flash rate configured at the panel before applying any coverage figure.
  • Where the YBO-BSB2 is used as a VdS compliant visual alarm device, Hochiki specifies device spacing directly: 2.0–2.2 m for YBO-BSB2/RL and 1.38–1.75 m for YBO-BSB2/WL, sited so the light coverage of each device overlaps to the centre of any adjoining device.
  • Do not derive a floor area from a beam angle. Use the published volumetric coverage or the published spacing.

Practical tips

  • Do not apply CHQ-WSB2 coverage information to YBO-BSB2, or vice versa, without checking the exact model documentation.

  • Confirm the exact device code, LED colour, mounting position and installation height before using a coverage value or formula.

  • A YBO-BSB2 fitted with an SI/CAP2 cap becomes a wall sounder beacon. Mounting position and orientation are part of the declared category O coverage, so confirm the coverage for the orientation you are actually installing.

  • If the device is to be fitted with a weatherproofing kit, check the ingress rating and the mounting arrangement first. See Which IP rating do I need for a wet or wash-down fire alarm installation? The kit changes the mounting arrangement, and mounting position and orientation are part of the declared category O coverage.

When to contact technical support

Contact Hochiki technical support if the application note does not cover your mounting position, orientation or installation height, if you need a category C or W rated device because the design requires a stated ceiling diameter or room width, or if a specifier asks for a coverage floor area that the O rating does not provide.

Safety note

This article is general guidance for Hochiki Europe products. Design, installation, commissioning, maintenance and modification of fire detection and alarm systems should be carried out by, or under the responsibility of, a competent person in accordance with the applicable standards (for example BS 5839-1 in the UK). Statutory requirements imposed by the relevant enforcing authority also apply. Always refer to the current product manual and data sheet for the exact model before carrying out any work.

References

  • CHQ-WSB2 Specification (ISS5 JUL26)
  • YBO-BSB2 Specification (ISS6 JUL26)
  • Application Note 132 — CHQ-WSB2 Wall Sounder Beacon Light Coverage (AP132 ISS2 MAR20)
  • Application Note 133 — YBO-BSB2 Base Sounder Beacon Light Coverage (AP133 ISS4 APR26)

Last reviewed: 2026-10-13 — Reviewed by: Hochiki Europe Technical Support