Rosemount 625IR Fixed Gas Detector, Emerson 625IR Infrared Point Gas Detector for Methane and Propane

What is the Rosemount 625IR fixed gas detector?

The Rosemount 625IR is a fixed infrared gas detector from Emerson that measures combustible hydrocarbon gas at the point where it is installed. It detects gas by dual band optical absorption with a solid-state, temperature compensated infrared sensor, and Emerson sets it up at the factory for either methane or propane with 100% LEL as the top of the range. The reading leaves the detector as a 4-20 mA signal with HART, and a separate RS-485 Modbus RTU port carries condition monitoring data.

The body is 316 stainless steel, the optics are heated so moisture does not settle on the optical surfaces, and a multi-colored LED on the front shows status. Emerson lists the 625IR as an active product, certified to SIL2, with a 5-year limited warranty and a 15-year warranty on the IR source.

Selection note: The 625IR is calibrated at the factory and, per Emerson, cannot be calibrated in the field. The detector keeps cross checking its own infrared sources and receivers and corrects itself, which is why Emerson specifies no zero or span drift. What stays on the maintenance plan is a 5-year proof test interval and gas free function testing, for which Emerson sells the 00625-9200-0001 gas free tester (methane, 50% LEL).

What are the Rosemount 625IR specifications?

Detection technology	Dual band optical absorption; solid-state infrared, temperature compensated
Gases (factory configured)	Methane (default) or Propane (option G02)
Measuring range	0-100% lower explosive limit (LEL)
Response time	T90 = 2 seconds (with environment shield); T90 < 1 second (without environment shield)
Accuracy	±2% full scale (FS), specified at +77 °F (+25 °C)
Repeatability	±1% FS
Drift	No zero or span drift
Calibration	Calibrated at the factory; cannot be calibrated in the field
Start-up time	< 2 minutes above -4 °F (-20 °C); < 20 minutes below -4 °F (-20 °C)
Analog output	Current source or sink 4-20 mA, HART digital communication
Serial port	RS-485, Modbus Remote Terminal Unit (RTU) for condition monitoring
Status indicator	Multi-colored LED indicator light on the front of detector
Supply voltage	18-32 Vdc
Power consumption	< 3 W average (standard configuration); < 5 W average (Arctic configuration)
Start-up current	In-rush current is limited to 1A
Cable entry	¾ NPT
Maximum conductor size	2.5 mm2 (stranded), 4 mm2 (solid)
Operating temperature	-40 to +167 °F (-40 to +75 °C)
Storage temperature	-40 to +167 °F (-40 to +75 °C)
Humidity	0 to 99 percent relative humidity
Vibration	Tested per IEC 60079-29: 10-31.5 Hz, 0.5 mm peak displacement; 31.5-150 Hz, 2G; 5-100 Hz, 4G
Housing material	Stainless steel 316
Ingress protection	IP66 and IP67, NEMA 4X
Weight	F02 standalone: 8.27 lb. (3.75 kg); F03 5.9-inch (15 cm) duct: 8.82 lb. (4 kg); F04 13.8 in. (35 cm) duct: 9.37 lb. (4.25 kg)
Warranty	5 (five)-year limited warranty; IR source warranty: 15 (fifteen) years

Maintenance note: Cold weather changes two figures. Start-up takes under 2 minutes above -4 °F (-20 °C) but up to 20 minutes below it, and the Arctic configuration raises average power from < 3 W to < 5 W, which matters when sizing an 18-32 Vdc supply for many detectors.

Where is the Rosemount 625IR used, and when is another Emerson model the better fit?

Emerson lists the 625IR for any hazardous area where hydrocarbon gas may be present. The named applications cover onshore and offshore oil and gas process facilities and pipelines (including FPSO and FLNG vessels), refining, chemical and petrochemical plants, power generation, tank storage and offloading, gas filling and distribution terminals, and gas transport. For ducts, Emerson offers long probe versions: F03 with a 5.9-inch (15 cm) extension and F04 with a 13.8-inch (35 cm) extension, plus duct flange kits.

The 625IR reads gas at one point. Where the site needs something else, another Emerson detector in this range fits better:

• Gas crossing a line, not a point: the Rosemount 935 open path combustible gas detector sends infrared from a source to a receiver at installation distances up to 660 ft. (200 m) and reads in LEL.m.
• Toxic gas on a perimeter: the Rosemount 936 open path toxic gas detector uses ultraviolet technology to watch for hydrogen sulfide or ammonia.
• Pressurized leaks in ventilated outdoor areas: the Rosemount Incus ultrasonic gas leak detector listens for the ultrasound of the release itself, so it reacts to toxic, combustible or inert gas.
• Field calibration and a local display: the Rosemount 925FGD fixed gas detector pairs a 925 transmitter and its local operator interface with a Rosemount 625ND NDIR sensor that can be calibrated in the field or off-site.
• No cable to the point: the Rosemount 928 wireless gas monitor runs on a power module and reports over WirelessHART.

Selection note: Emerson’s data sheets give these figures side by side. 625IR: T90 = 2 seconds with the environment shield, 0-100% LEL, < 3 W average, factory calibration only. 925FGD with 625ND sensor: T50 < 7 sec and T90 < 10 sec for methane, propane, ethylene, n-butane and ethane, maximum 2.4 W with heater off, field or off-site calibration. 935 open path: response time < 2 seconds, 0 to 5 LEL.m methane and propane, typical draw 220 mA (detector) and 240 mA (source).

Which approvals, outputs and documents apply to the Rosemount 625IR?

The 625IR ordering table offers these product certification codes, printed as Emerson words them:

E1	ATEX Flameproof
E2	Brazil Flameproof INMETRO
E7	IECEx Flameproof
E5	US Explosion-proof
E6	Canada Explosion-proof
KS	USA, Canada, ATEX, and IECEx Explosion-proof

Emerson states the 625IR is certified to Safety Integrity Level (SIL2) functional safety standards. The certificate itself (IEC 61508, SIL2) ships only when option QT is ordered, and the calibration certificate only with option Q4. The full certification markings are not in the data sheet: Emerson refers to the Rosemount 625IR Quick Start Guide for them, so name the marking you need when you ask for a quote.

Outputs: current source or sink 4-20 mA with HART, RS-485 Modbus RTU and the front status LED. Source mA is the default; option SK sets sink mA.

Documents: Rosemount 625IR data sheet, December 2025, MS-00813-0100-3625 Rev AG and the Rosemount 625IR page on Emerson.com. For background on point, open path and ultrasonic detection, see the PE Energy gas detection systems guide.

Installation note: Emerson built the 625IR electronics to tolerate power-up with terminal wires accidentally swapped, and in-rush current at start-up is limited to 1A. Under the IEC 60079-29 vibration test the device stays within ±5 percent of measuring range or ±10 percent of indication, with no fault signal and no false alarms.

How do I request a quote for the Rosemount 625IR?

Send PE Energy the full Emerson model code if you have it. If not, these are the choices the 625IR ordering table asks for:

Gas type and range	F02 standalone; F03 duct mount 5.9-inch (15 cm) extension; F04 duct mount 13.8-inch (35 cm) extension (all hydrocarbon gases, 0-100% LEL)
Housing	S1 Stainless steel, ¾-inch NPT male thread connection
Product certification	E1, E2, E7, E5, E6 or KS
Calibration gas	Methane (default) or G02 Propane
Calibration gas standard	NFPA (2017) default, or IEC for IEC/ISO LEL standards
Analog output	Source mA (default) or SK sink mA
Gas nozzle	Included by default; GN0 if not required
Certificates	Q4 calibration certificate; QT SIL2 certificate

Add accessories (see the next section) and quantity. PE Energy confirms price, availability and lead time with the quote. Request a Rosemount 625IR quote from PE Energy.

Model code example: Emerson’s sample code 625IRF02S1E1Q4QT reads as 625 (gas detection sensor), IR (standalone optical infrared sensor), F02 (hydrocarbon gases 0-100% LEL, standalone), S1 (stainless steel, ¾-inch NPT male thread), E1 (ATEX Flameproof), Q4 (calibration certificate) and QT (SIL2 certificate for IEC 61508). With no G02, SK or GN0 in the code, that detector is calibrated for methane, sources mA and ships with the gas nozzle.

Which Rosemount 625IR accessories fit which installation?

Emerson lists 625IR accessories by part number. The most useful ones, grouped by the job they do:

Pole mounting	00625-9200-0102 2-inch pole mounting kit; 00625-9200-0003 mounting plate kit for 3-inch and 4-inch poles
Sun, weather, insects	00625-9200-0005 sunshade; 00625-9200-0021 environment shield; 00625-9200-0034 environment cap; 00625-9200-0006 mosquito net
Duct flanges	00625-9200-0024 DIN 150 PN6; 00625-9200-0025 DIN 200 PN6; 00625-9200-0026 JIS 150 5K; 00625-9200-0027 JIS 200 5K; 00625-9200-0028 clamping version
Testing	00625-9200-0001 gas free tester; 00625-9200-0011 remote bump test kit; 00625-9200-0012 handheld bump test housing
Sampling	00625-9200-0010 aspiration kit (sample housing)

Installation note: Fitting the environment shield is a trade-off Emerson quantifies: T90 = 2 seconds with it against T90 < 1 second without. Where gas must be drawn to the detector instead of reaching it by diffusion, the aspiration kit is the listed option, and duct installs pair an F03 or F04 detector with one of the duct flange kits.