Edwards SIGA-DDOS — the Optica Intelligent Duct Smoke Detector, a Signature Series addressable duct detector built specifically for the moisture and dust conditions of HVAC ductwork.
The optical sensing tube uses the same principles as the Optica open-area detector: analog information from the smoke sensing elements is converted to digital signals, then measured and compared against historical readings and time patterns, with digital filters and algorithms removing signal patterns that are not typical of fires. Construction is aimed squarely at duct survival — separate sensing and control sections, an optical sensing tube, conformally coated circuit boards and hydrophilic coatings keep contaminants away from sensitive electronics. Differential sensing prevents gradual environmental change from shifting alarm sensitivity, while a rapid change such as smoke from a fire triggers an alarm.
Air enters through a sampling tube that extends into the duct and returns through an exhaust tube, the pressure difference between them drawing the sample through the chamber. The exhaust tube is included; the sampling tube is ordered separately.
Specifications
| Detection method |
Photoelectric (light scattering principle) |
| Sensitivity |
1.5 to 4.5 %/ft obscuration |
| Air velocity rating |
100 to 4,000 ft/min, meeting the required minimum air pressure differential |
| Air pressure differential |
0.01 to 0.83 inch of water |
| Operating voltage |
15.2 to 19.95 VDC |
| Operating current |
Standby 50 µA; alarm 60 µA |
| Common alarm relay |
One Form C, unsupervised and power-limited; 3.0 A at 30 VDC, 3.0 A at 120 VAC (0.35 pf), 1.5 A at 240 VAC (0.35 pf) |
| Alarm test response time |
5 seconds |
| LED indicators |
Alarm (red), test (amber), normal (green) |
| Operating temperature |
UL/ULC: -20 to 158°F (-29 to 70°C) |
| Relative humidity |
0 to 93%, noncondensing |
| Storage temperature |
-20 to 158°F (-29 to 70°C) |
| Dimensions |
7.75 x 6.1 x 2.5 in. (see installation note regarding the metric figure) |
| Wire size |
14 to 22 AWG |
| Compatible panels |
Edwards Signature loop controllers |
| Agency listings |
UL, ULC, CSFM (3242-1657:0527), FM |
| Ship weight |
2.4 lb (1.1 kg) |
Installation notes
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Drop-in retrofit from SuperDuct: the Optica duct detector uses the Signature protocol and the same entry and exit pipe locations and dimensions as the SuperDuct detectors, with standard sampling tube spacing, so an existing SIGA-SD installation can be migrated without re-cutting the duct.
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Sampling tube is ordered separately: the exhaust tube is supplied; the sampling tube is not. Size it from SD-T8 through SD-T120 — the same tube range used by the SuperDuct detectors.
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Caution on one accessory row: the ordering table lists SD-T78 as an “8-inch sampling tube,” the same description given to SD-T8, while its shipping weight of 7.5 lb (3.4 kg) is consistent with a 78-inch tube. Treat the SD-T78 description as a typographical error in the data sheet and confirm length when ordering.
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The metric dimension does not match the imperial one: the specification table gives 7.75 x 6.1 x 2.5 inches as “167 x 155 x 65 mm,” and the drawing callout gives 7.75 in. as 16.69 cm. 7.75 inches is 19.7 cm, not 16.7 cm, so the long dimension’s metric conversion is wrong in both places; the 6.1 in. / 155 mm and 2.5 in. / 65 mm figures do convert correctly. Use the inch values.
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Tube orientation: sampling tubes must be installed with the inlet holes facing the airstream and may be rotated in 45-degree increments, allowing the unit to be mounted at virtually any angle relative to airflow. The sampling tube can be installed from the duct side or from inside the sensor compartment; the exhaust tube must be installed from the duct side.
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Verify the duct before installing: Edwards directs that duct air velocity, temperature and humidity be tested first to confirm they are within the detector’s operating range. The SD-VTK air velocity test kit is available for this.
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Duct detectors have limits: a duct detector is not a substitute for an open-area smoke detector, not a substitute for early warning detection, and not a replacement for a building’s regular fire detection system. It will not operate without electrical power.
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Remote indication: where the detector’s controls and indicators are hidden from view, a remote test station or an LED indicator can be connected. Maximum resistance on that wiring is 10 ohms per wire.
Related models
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SIGA-SD — the SuperDuct predecessor. It is a different instrument, not just an older label: 0.79 to 2.46 %/ft sensitivity against the DDOS’s 1.5 to 4.5 %/ft, a 2.0 A Form C relay against 3.0 A, and 0.005 to 1.00 in. water pressure differential against 0.01 to 0.83 in.
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SD-TRM / SD-TRK — magnetic and keyed remote test/reset stations providing alarm test, trouble indication and reset from a remote location.
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SIGA-LED — remote alarm LED (3 VDC, 30 mA max).
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SIGA-DDOSIB / SIGA-DDOS-ROT / DDOS-RET — replacement interface board, replacement optical sensor tube assembly, and replacement exhaust tube.
Specifications taken from the Edwards data sheet “Optica Intelligent Duct Smoke Detector — Signature Series SIGA-DDOS,” document E85001-2006, Issue 1.1 (08-05-25). Manufacturer specifications are subject to change without notice.
