Dahua DHI-HY-SA21A-W2 | Wireless Photoelectric Smoke Alarm – Battery-Powered, Split-Spectrum Sensor

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. 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. Insert a fresh CR123A lithium battery before commissioning and make a note of installation date—this helps scheduling future replacements (approx. every 3 years). Press the test/silence button after installation to confirm the alarm output and LED indicators are functioning correctly. 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. Ensure the device is not blocked by furniture, partitions, or drapes; the smoke intake must remain unobstructed for correct operation. Avoid installing directly above cooking appliances or air vents where steam or strong drafts may trigger nuisance alarms; use manufacturer guidance on exclusion zones. 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. 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.   SKU: DHI-​HY-​S‌A21A-​W2 Categories: Dahua, Dahua Airshield Wireless Alarms Tags: dahua alarms, dahua Wireless keyfob, dahua wireless remote control, DHI-ARA24-W2, Wireless keyfob