UV/IR Flame Detector 3986

UV/IR Flame Detector - Model 3986 

The model 3986 UV/IR flame detector is designed to detect unwanted fires and output appropriate alarm information. The model 3986 senses ultraviolet radiation and infrared radiation in the appropriate wavelengths for very early fire detection. Using the patented Fire Event Analysis (FEA) algorithm, it is also able to distinguish between real fire and non-fire events providing superior false alarm immunity. The technology has proven itself over decades of reliable service.

The model 3986 is available in two versions, one for hydrocarbon fires only, and one for hydrocarbon and certain non-hydrocarbon fires. This dual capability provides the unique capability of providing fire detection for a broad range of fuels with a single unit. Both versions are available with an automatic self-test function to monitor the detector’s ability to sense fires and report a fault condition when impaired.

Typical applications for the model 3986 UV/IR flame detector are:

  • Refineries
  • Turbine enclosures
  • Petrochemical plants
  • Tank farms
  • Power plants
  • Compressor stations
  • LPG /LGN facilities
  • Hangars
Uv/ir flame detector

Senses UV and IR radiation for extremely fast fire detection


Fire event analysis algorithm for superior false‑alarm immunity


120° field of view and over 250ft long range detection


Automatic through-the-lens diagnostic self-test


Crafted with decades of real-world experience to simplify the installation, commissioning, maintenance 

Model Number


Spectral Response

Ultraviolet: Peak sensitivities of 0.22 μm
Infrared: Peak sensitivities of 4.4 μm (standard), Peak sensitivities of 2.9 μm and 4.4 μm (dual pass)

Performance Ratings 

Responsive to Flame Types:

  • hydrocarbon (gas, propane, methane, alcohol, JP-4, JP-3, etc.)
  • non-hydrocarbon (hydrogen, silane, hydrazine, etc.) when dual-pass IR sensor is used

3rd Party Certified to Detect:

  • Saturating signal source in 50 millisec
  • 1 sq. ft. gasoline fire at 50 ft. in 1 sec
  • 4 sq ft aviation fuel fire at 100 ft in 5 sec or less
  • 100 sq ft aviation fuel fire at 250 ft in 5 sec or less
  • Methane plume flame at 35 ft in 1 sec

Dual-pass Infrared Sensor:

  • Silane plume flame 24 in at 35 ft in 60 millisec
  • Hydrogen plume flame 20 in at 35 ft in 3 sec
  • Hydrazine 8 in pool fire at 80 ft in 9.4 sec

Operating Temperature Range

-40℉ to 185℉ (-40℃ to 85℃)

Mechanical Specifications

Weight: (aluminum) 2.4 kg (5 lbs)
Weight: (stainless steel) 6.3 kg (13 lbs)
Height x width x depth: 114 x 140 x 153 mm (4.5 x 5.5 x 6.0 in)
Conduit entry: 3⁄4-14 NPT or M20-1.5

Detector Inputs 


  • Nominal voltage: 24 VDC (ripple voltage <240mV)
  • Range: 20 to 30 VDC

Power consumption:

  • Standby: 90 mA
  • Alarm: 110 mA
  • Auto and manual text: 250 mA

Detector Outputs

  • Relays (2): fire, trouble, dry contacts, hermetically sealed 
  • Rated: 2A at 28 VDC. User selectable NO or NC
  • Fire relay: user selectable latching or non-latching

Environmental Ratings

Class I, Division 1, Groups B, C & D (explosion proof)
Class II, Division 1, Groups E, F & G (dust ignition proof)
Type 4X weatherproof, dust-tight, watertight CE0081 II 2 G/D
Ex db IIB+H2 T5 Gb for gas
Ex tb IIIC T100°C Db IP66 for dust


Part No. - Description:

3900-01 - SS Tilt mount for Aluminum Enclosure
3900-02 - SS tilt mount for Stainless Steel Enclosures
3900-04 - Air Shield Model
3900-05 - SS Sun Shade/Rain Guard
3900-06 - UV/IR Tester 
3900-07 - Universal Tester 
3900-08 - Battery Pack for tester  # 3900-06, 3900-07
3900-09 - Charger for tester # 3900-06, 3900-07
3900-14 2" Pole Mount kit for # 3900-01 bracket
3900-15 2" Pole Mount kit for  # 3900-02 bracket

 Sentry IT Fire and Gas Detection Solutions

A brief introduction to the sales, design and manufacturing facilities for Sierra Monitor Corporation's Sentry IT fire and gas solutions.