A four-sensor portable multi-gas detector priced at US $295-310 typically covers O2, LEL, H2S and CO in one instrument, while a single-gas handheld for one species such as H2 or PH3 lists at US $150-160 in current Chinese OEM catalogs.
Single-gas units are built around one electrochemical, pellistor, NDIR or PID cell, whereas multi-gas detectors stack 2-4 sensor channels inside the same enclosure, share one microcontroller and drive one audible/visual alarm tree; the channel count is the single largest driver of both unit price and calibration workload.
Sensor-Count Math: One Species vs 2-4 Channels
The K60-IV ships as a four-sensor portable with slots for oxygen, combustible gas (LEL), hydrogen sulfide and carbon monoxide in one compact housing [S1]. The "Multi-parameter Gas Detector" listing for coal-mine and tunnel work targets the same quartet - CO, H2S, O2 and CH4 - and adds an upper/lower limit alarm on each channel [S3].
By contrast, the Henan Inte catalog breaks the single-gas family into dedicated SKUs per species: a handheld PH3 detector for fumigation at US $295-310 / 5-piece MOQ, an H2 meter at US $150-160 / 1-piece MOQ, and an ETO / C2H4O leak detector listed as a portable single-channel unit. The "one sensor, one species" architecture keeps calibration simple - you swap or span one cell instead of four - but it forces the worker to carry one instrument per hazard.
For most plant safety officers, the channel count is dictated less by preference than by the confined-space rule set, which typically requires simultaneous monitoring of O2, LEL and at least one toxic when entering a vessel; a single-gas unit cannot meet that with one channel.
Form Factor and Deployment Pattern
Single-gas detectors are almost always handheld or clip-on, designed for one worker, one hazard, one shift - the H2, PH3 and ETO units in the Henan Inte line are all explicitly "handheld" / "portable" form factors. Multi-gas detectors come in two flavors: the pocket-portable four-sensor brick typified by K60-IV [S1] and the SCOTT Scout (SCT096-2560) covering O2, CO, H2S and LEL as CH4 [S2], and the older Sperian Biosystem Multipro remote-sampling configuration (MPN 54-49-102), which pulls the gas sample through a pump and probe to the sensors [S6].
Fixed single-gas detectors are a separate category, typically wall-mounted with 4-20 mA or RS-485 output for SCADA tie-in; the Henan Inte fixed Cl2 sensor for WWTP service runs US $240-270 / 1-piece MOQ and advertises both 4-20 mA and RS-485 outputs in the same SKU. gas detector and fixed gas detector are the two encyclopedia anchors that map onto this fixed-vs-portable split. A multi gas detector housing, on the other hand, almost always implies the portable four-sensor brick rather than a fixed wall unit.
Decision Criteria: Hazard Count, Mobility and Cost-per-Channel
Three gates decide the build. Hazard count: if the work order names more than one toxic or combustible species plus oxygen, the multi-gas path wins on instrument count alone. Mobility: handheld single-gas units weigh less and run longer on a charge because they power one cell, but workers in a multi-hazard space still need to carry several, defeating the size advantage. Cost per monitored channel: the Henan Inte four-gas family at US $295-310 versus four single-gas handhelds at US $150-310 each changes the math at the second hazard. [S1]
The China wholesale market for "4 Gas Detector" SKUs lists CE-certified portable units starting around US $7.30-8.50 per piece at 10-piece MOQ from suppliers such as Hebei Zehong Technology [S4]; that price band, however, is the household-leak-detector tier, not the industrial LEL/CO/H2S/O2 brick, and the certification language ("contact issuer for current status") flags it as a check-before-you-buy line item.
A combustible gas detector as a standalone makes sense when LEL is the only concern - tank farms, LNG stations, natural-gas utilities - while a toxic gas detector alone fits a process where one specific species (Cl2 in a water-treatment plant, NH3 in a refrigeration room, H2S in a sewer) is the only credible acute hazard. The moment two or more of those hazard classes share a work area, the four-sensor brick is the lower instrument-count, lower training-overhead answer.
Portable vs Fixed: When the Multi-Gas Is the Wrong Choice
Multi-gas detectors are built for the worker, not the process. A fixed-point installation - chlorine room, ammonia compressor skid, H2S-prone separator - is almost always served by a dedicated fixed sensor on 4-20 mA or RS-485, not by a portable unit clipped to a belt. The portable path also loses on sensor life: a pellistor LEL cell and three electrochemical cells in one housing must all reach end-of-life together, while a fixed installation can swap the cell that fails first. [S2]
For confined-space entry, the portable gas detector class - whether single-gas or four-sensor - is mandatory before break-open, and bump-testing before each shift is the industry norm; a multi-gas unit cuts that bump-test from four separate procedures to one. By contrast, area monitors on a refinery perimeter are typically single-gas fixed units, one per species, because the perimeter does not need a worker-mobility form factor and benefits from per-channel 4-20 mA into the DCS.
Price Bands and MOQ Reality (2026-05 / 2026-06 data)
Concrete price points from current 2026 OEM catalogs: Henan Inte single-gas handheld H2 detector US $150-160 / 1-piece MOQ, handheld PH3 detector US $295-310 / 5-piece MOQ, fixed Cl2 sensor US $240-270 / 1-piece MOQ; the K60-IV four-gas portable listed on the Nanjing KELISAIKE product page as a compact four-sensor build [S1]; "Multi-parameter Gas Detector" coal-mine SKU shipped on a 7-day delivery window [S3].
On the secondary market, used MSA ALTAIR 4X multi-gas detectors list in the US $599 band (new open-box condition), Sperian Multipro multi-sensor units with sampling pump at roughly US $199.95 plus shipping [S6], and Drager Model 31 V-100 cm3 multi-gas detector pumps at US $55.29 used. Those secondary numbers are useful for benchmarking sensor-platform longevity - Drager, MSA, Sperian and SCOTT are the four names that consistently appear on the used market for multi-gas bricks, and that consistency itself is a sourcing signal worth tracking.
Selection Rule of Thumb and the 2026 Watch-List
Pick single-gas when one named species is the only credible acute hazard and the worker stays outside a confined space. Pick multi-gas when the entry permit, the SOP or the JHSEA names two or more of O2, LEL, CO or H2S as simultaneous monitoring requirements. Pick fixed over portable when the hazard is tied to a process point, not a worker. Watch two signals over the next sourcing cycle: the price spread between Henan Inte-type Chinese OEM handhelds and the Drager/MSA/Sperian used-market residuals, and the CE/ATEX certificate language on China wholesale listings - "contact issuer for current status" is the line that should make any industrial buyer pause before issuing a PO [S4].
For related coverage, see Theodolite 2026 Price & Cost Guide: Optical, Electronic and Total-Station Cost Bands.