The Dahua DHI-HY-SA21A-W2 wireless smoke alarm is designed for flexible, reliable fire detection in settings such as villas, apartments, retail shops or rental properties. With its photoelectric (split-spectrum) sensor it detects visible smoke particles early, reducing false-alarms from steam or cooking.
Powered by a replaceable 3 V CR123A lithium battery, the unit requires no mains wiring, making it ideal for retrofit installs or where limited wiring is available. Its compact design (approx. φ98 mm × H43.1 mm) supports ceiling mounting and the unit weighs approx. 140 g.
Key features include: loud audible alarm of 85-90 dB(A) at 3 metres, a combined test and silence button for user convenience, low-battery warning, a fault-warning indicator, and a coverage area of roughly 20–40 m² when ceiling height is under 8 m. The unit is rated for operation between -10 °C and +55 °C and humidity up to 95% (non-condensing).
For rental properties, this alarm offers a low-maintenance, easily replaceable unit that avoids rewiring and reduces tenant disruption.
Specifications
| Feature |
Specification |
| Collection Type |
Smoke |
| Sensor Type |
Photoelectric (split-spectrum) |
| Sampling Period |
10 s |
| Alarm Type |
Smoke alarm, fault warning, low battery warning |
| Alarm Volume |
85 dB-90 dB(A) at 3 metres |
| Silence Function |
Yes (via test/silence single button) |
| Alarm Response Threshold |
0.2 dB/m – 0.3 dB/m |
| Coverage Area |
Approx. 20 m² to 40 m² (ceiling height <8m) |
| Power Supply |
3 V CR123A lithium battery (replaceable) |
| Monitoring Current |
≤ 35 µA |
| Alarm Current |
≤ 35 mA |
| Battery Life |
Approx. 3 years |
| Operating Temperature |
-10 °C to +55 °C |
| Operating Humidity |
≤ 95% RH (non-condensing) |
| Dimensions |
φ98 mm × H43.1 mm |
| Weight |
Approx. 140 g |
| Mounting |
Ceiling mount |
| Indicator Lights |
Green & red LED indicating standby/ alarm/ fault/ low battery |
| Case Material |
ABS plastic |
| Colour |
White |
Installer Tips
-
Mount the unit on the ceiling (or on the wall if ceiling not possible) in the centre of the protected zone where possible, avoiding corners or immediately next to walls.
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Ensure the ceiling height is under 8 metres to achieve the specified coverage area; if higher, spacing between devices should be reduced or additional units should be used.
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Insert a fresh CR123A lithium battery before commissioning and make a note of installation date—this helps scheduling future replacements (approx. every 3 years).
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Press the test/silence button after installation to confirm the alarm output and LED indicators are functioning correctly.
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When used in a rental property, record device serial number and installation date in the tenant-handover documentation; explain the silence button function to occupants.
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Ensure the device is not blocked by furniture, partitions, or drapes; the smoke intake must remain unobstructed for correct operation.
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Avoid installing directly above cooking appliances or air vents where steam or strong drafts may trigger nuisance alarms; use manufacturer guidance on exclusion zones.
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Replace the device immediately if it enters low-battery or fault condition (red LED flashes once per minute).
-
Check the device annually (or as per local regulation) by pressing test button and verifying alarm sound and LED status.
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Inform tenants of the silence function and that pressing the test/silence button will temporarily quiet the alarm for about 12 minutes—ensure they know the fire risk is still present.
Frequently Asked Questions (FAQs)
Q: Is this device mains-wired or battery-operated?
A: It is battery-operated, using a replaceable 3 V CR123A lithium battery, so no mains wiring is required.
Q: What type of sensor technology does it use?
A: It uses a photoelectric sensor with split-spectrum technology, which improves early detection of real smoke and reduces false alarms from cooking or steam.
Q: What is the expected battery life?
A: About 3 years under normal conditions, subject to ambient temperature and usage of the test/silence button.
Q: Can the alarm be silenced temporarily?
A: Yes. The combined test/silence button allows the user to silence the alarm temporarily (for around 12 minutes) after a non-critical event.
Q: What area does one device cover?
A: With ceilings under 8 m in height, each device can protect approx. 20–40 m²; larger spaces may require additional devices.
Q: Does it have LED indicators?
A: Yes. A green LED flashes once per minute when in standby, a red LED flashes once per second in alarm condition, and once per minute in fault/low-battery condition.
Q: What ambient conditions does it tolerate?
A: Operating temperature from -10 °C to +55 °C, and humidity up to 95% non-condensing.
Q: Where can this device be mounted?
A: Ceiling mount is recommended. In some jurisdictions wall mounting is permitted but check local regulations.
Q: Is it suitable for rental properties?
A: Yes. Its battery-powered design, ease of installation and minimal wiring make it ideal for rental dwellings, avoiding mains modifications.
