IREX Infra-red pellistor replacement flammable gas detector

General Details

IREX is a sinter-free, fully featured infrared gas detector that produces an mV Wheatstone Bridge output as used on conventional pellistor based systems.

IREX replaces old pellistor heads by simply mounting on the original junction box and connecting to the original cable. The IREX concept enables upgrade to dual-wavelength IR gas detector technology without incurring the very significant costs associated with replacing the control system and re-installation.

IR Technology versus Pellistor

Pellistors do not fail safe Sensors can be ‘poisoned’ and rendered insensitive to gas by silicones, lead, sulphurs and chlorinated compounds.
Pellistors are high maintenance Sensors must be regularly tested with gas to ensure they are stilloperational. Sensors typically last 3-5 years, after which they must beexchanged.
Pellistors must be operated behind a sinter (flame arrestor) Sinters may become blocked, thus preventing gas from reaching thesensor.
Pellistors may burn out If exposed to gas concentrations in excess of 110% LEL.
Pellistors need oxygen Their ability to detect gas reduces significantly in oxygen deficientatmospheres.

Low power

  • IREX consumes less than 1W of power – ensures compatability with a wide range of control systems


  • Independantly tested for reliability and performance in harsh offshore conditions by Micropack Engineering Ltd – demonstrates IREX will operate dependable in any application
  • 3rd party approval to the performance standard EN60079-29-1
  • Employs sophisticated systems and algorithms – ensures reliable operation at all times
  • T90 response time of less than 4 seconds – rapid indication of hydrocarbon gas hazards
  • Optical components are treated with a STAY-CLIR coating – prevents partial obscuration in condensing atmospheres

Easy to maintain

  • No adjustments are necessary at the detectors, zero and span adjustments (if required) are performed at the control panel only – saves significant time and cost
  • Test can be applied remotely via a tube to the standard weather cover
  • Sinter-free operation – unlike a pellistor sensor, there is no risk of a sinter becoming blocked
Size 120 x 55 x 130mm (1.7 x 5.1 x 3.3ins) (with spigot gland)
Weight 1.5kg (10.8oz)
Ingress protection IP66
Enclosure material 316 stainless steel
Power 800mW nominal
Connection Supplied either with M20 spigot gland for insallation into existing junction
boxes or with one M20 cable gland entry
Operating voltage and current 3Vdc nominal (2.9-3.2Vdc)
260mA nominal (260-280mA)
Electrical output 3-wire mV (Wheatstone) Bridge. Typically 10-20mV per % vol. methane
Operating temperature -40°C to +75°C
Humidity 0 to 100% RH non-condensing
Repeatability +/- 2% FSD
Zero drift +/- 2% FSD per year maximum
Response time T-90
Performance Tested in accordance with EN60079-29-1
Functional safety Validation to IEC61508 SIL 2
Approvals II 2 G Exd IIB + H2 T6 (-40 to +50°C) T4 (-40 to +75°C)
EMC compliance EN 50270, FCC, ICES-003


For a full list of Gases see the datasheet on the Documents tab.