{"product_id":"watchgas-sst1-replacement-ch4s-sensor-sst-spare-mm","title":"WatchGas SST1 Replacement CH4S Sensor SST-SPARE-MM","description":"\u003cp\u003e\u003cstrong\u003eWhen your methanethiol sensor drifts, you don't replace the whole monitor. You swap the sensor cell.\u003c\/strong\u003e\u003c\/p\u003e\n\n\u003cp\u003eThat's the operational advantage of the serviceable WatchGas SST1 line. Traditional single-gas monitors are single-use — when the sensor reaches end-of-life or a bump test reveals unrecoverable drift, the whole unit gets discarded. The SST1 platform is designed to be maintained: this WatchGas Replacement CH4S Sensor drops into the \u003ca href=\"https:\/\/pksafety.com\/products\/watchgas-sst1-serviceable-ch4s-gas-detector-sst1-mm\"\u003eWatchGas SST1-MM Serviceable CH4S Gas Detector\u003c\/a\u003e and any WatchGas SST4-series multi-gas monitor configured with a CH4S sensor slot.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eYou can smell methanethiol before you can measure it — but you probably can't smell it accurately for long.\u003c\/strong\u003e Mercaptans are one of the gases most likely to cause olfactory fatigue: the nose adapts within minutes, and the same worker who alarmed at the smell 20 minutes ago may not notice steady exposure now. And in mixed industrial environments — natural gas processing, wastewater digesters, Kraft pulping, animal agriculture — the smell often gets misattributed to a natural gas leak rather than the specific methanethiol exposure a monitor would quantify. Sensor accuracy at the ceiling limits (OSHA 10 ppm, NIOSH 0.5 ppm) is what determines whether the monitor catches drift the nose is missing.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhat this sensor is (and isn't):\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eIt IS\u003c\/strong\u003e a factory replacement CH4S (methanethiol \/ methyl mercaptan) electrochemical sensor cell for the serviceable SST1-MM monitor and any WatchGas SST4-series multi-gas monitor configured with a CH4S sensor slot. Note that the SST4 platform's \u003cem\u003estandard\u003c\/em\u003e 4-gas sensor set is LEL\/O2\/CO\/H2S — CH4S is a custom configuration on SST4 monitors, not the default.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIt is NOT\u003c\/strong\u003e a standalone gas detection device. The sensor cell requires a compatible WatchGas SST monitor to function.\u003c\/li\u003e\n\u003cli\u003eThe WatchGas SST1 line does NOT include Limited-Life (2-year or 3-year alert-only) monitors for methanethiol, so — unlike H2S, CO, and O2 replacement sensors — there's no non-serviceable variant to exclude from the compatibility list.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003e\u003cstrong\u003eAbout the sensor:\u003c\/strong\u003e solid polymer electrochemical technology, 0–100 ppm detection range, 1-year sensor warranty. The 1-year warranty is shorter than the 2-year standard on other WatchGas SST replacement sensors — mercaptan-tolerant electrochemical cells have shorter useful life across the industry because the cell chemistry is more susceptible to drift and cross-sensitivity with structurally similar sulfur compounds. Factor the shorter warranty into your fleet's replacement cadence.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhen to replace a methanethiol sensor cell:\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eThe sensor fails a bump test and won't recover on recalibration\u003c\/li\u003e\n\u003cli\u003eCalibration drift exceeds acceptable tolerance across successive cal events, especially at the low ppm range where the NIOSH ceiling sits\u003c\/li\u003e\n\u003cli\u003eThe monitor displays a sensor fault code specific to the CH4S channel\u003c\/li\u003e\n\u003cli\u003eThe sensor's warranty period (1 year) has elapsed — for mercaptan sensors, proactive replacement at warranty end is often the right call given the shorter useful life\u003c\/li\u003e\n\u003cli\u003eYou're rotating a fleet's sensor generation on a proactive maintenance cadence — especially valuable in continuous-mercaptan environments (odorization plants, Kraft mills, biosolids digesters) where sensor drift can silently miss exposure events\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003e\u003cstrong\u003eWho buys the SST-SPARE-MM:\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eOwners of the WatchGas SST1-MM serviceable methanethiol monitor whose current sensor has drifted, failed a bump, or reached end-of-warranty\u003c\/li\u003e\n\u003cli\u003eNatural gas processing and odorization plant operators (methanethiol is added to natural gas as a safety odorant — accurate on-site monitoring at odorization stations is a chronic requirement)\u003c\/li\u003e\n\u003cli\u003ePetroleum refinery operators handling sour crude with thiol contaminants, or running mercaptan-removal units\u003c\/li\u003e\n\u003cli\u003eKraft pulp and paper mill supervisors (methanethiol is a Kraft process byproduct alongside H2S and dimethyl sulfides)\u003c\/li\u003e\n\u003cli\u003eWastewater treatment operators, especially at biosolids digesters and downwind of digester emissions\u003c\/li\u003e\n\u003cli\u003eAnimal agriculture facility managers (dairy and hog operations) with community-emissions exposure concerns\u003c\/li\u003e\n\u003cli\u003eLandfill operators with active gas capture and flaring systems\u003c\/li\u003e\n\u003cli\u003eRendering plants and other biological-waste-processing facilities\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003e\u003cstrong\u003eSensor specifications:\u003c\/strong\u003e\u003c\/p\u003e\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eGas\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cstrong\u003eRange\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cstrong\u003eSensor technology\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cstrong\u003eWarranty\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cstrong\u003eCompatible monitors\u003c\/strong\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCH4S (methanethiol \/ methyl mercaptan)\u003c\/td\u003e\n\u003ctd\u003e0–100 ppm\u003c\/td\u003e\n\u003ctd\u003eSolid polymer electrochemical (dry-cell)\u003c\/td\u003e\n\u003ctd\u003e1 year\u003c\/td\u003e\n\u003ctd\u003eSST1-MM, SST4-series (with CH4S sensor slot)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003cp\u003e\u003cstrong\u003eKey features:\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eHigh accuracy across the 0–100 ppm detection range\u003c\/li\u003e\n\u003cli\u003e1-year operational warranty (specialty-cell chemistry)\u003c\/li\u003e\n\u003cli\u003eUltra-low power consumption (optimized for battery-operated and IoT-integrated monitors)\u003c\/li\u003e\n\u003cli\u003eHigh precision at low methanethiol concentrations — critical for NIOSH REL-aligned monitoring (0.5 ppm ceiling)\u003c\/li\u003e\n\u003cli\u003eNo zero drift\u003c\/li\u003e\n\u003cli\u003eSilicone-resistant (no poisoning by common industrial silicone contaminants)\u003c\/li\u003e\n\u003cli\u003eDirect linearity across the detection range\u003c\/li\u003e\n\u003cli\u003eHigh temperature range tolerance\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003e\u003cstrong\u003ePK Safety services the full WatchGas SST line with factory-trained technicians in-house.\u003c\/strong\u003e If you'd rather send the monitor to us for sensor replacement than swap the cell yourself, we handle that in-house — full swap, calibration verification against a certified methanethiol standard, and return-to-service. We also service BW\/Honeywell (Factory Authorized Service Center), RKI, and RAE Systems monitors — one shop for a mixed-brand fleet's sensor lifecycle. Call us at \u003cstrong\u003e800.829.9580\u003c\/strong\u003e to talk through your methanethiol sensor replacement workflow with someone who understands the SST platform and specialty gas monitoring.\u003c\/p\u003e\n\n\u003cdiv class=\"specification\"\u003e\n\u003cp\u003e\u003cstrong\u003eTechnical documents (WatchGas SST1):\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003e\u003ca href=\"https:\/\/watchgas.com\/app\/uploads\/2024\/03\/SST1-brochure-1.1.pdf\" target=\"_blank\"\u003e\u003cimg border=\"0\" height=\"65\" width=\"63\" alt=\"Brochure\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0872\/5469\/6254\/files\/pdf-icon_ac4da377-e8e0-4a9c-9dcc-746269055096.png\"\u003e\u003c\/a\u003e \u003cstrong\u003eSST1 Brochure\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003cp\u003e\u003cstrong\u003ePart Number:\u003c\/strong\u003e WG01-SST-SPARE-MM — WatchGas Replacement CH4S (Methanethiol) Sensor (1-year warranty)\u003c\/p\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\n\u003cdetails open\u003e\n\u003csummary\u003eWhich WatchGas monitors is the SST-SPARE-MM sensor compatible with?\u003c\/summary\u003e\n\u003cp\u003eThe SST-SPARE-MM is compatible with:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/pksafety.com\/products\/watchgas-sst1-serviceable-ch4s-gas-detector-sst1-mm\"\u003eSST1-MM Serviceable CH4S Gas Detector\u003c\/a\u003e — the single-gas methanethiol monitor is designed around this sensor\u003c\/li\u003e\n\u003cli\u003eWatchGas SST4-series multi-gas monitors \u003cstrong\u003eonly when custom-configured with a CH4S sensor slot\u003c\/strong\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eThe SST4 platform's \u003cem\u003estandard\u003c\/em\u003e 4-gas sensor set is LEL\/O2\/CO\/H2S. CH4S is a specialty configuration — usually ordered for Kraft mill or natural-gas-odorization work where methanethiol monitoring is a primary requirement. If your SST4 has the standard config, this sensor won't fit. Call PK Safety at 800.829.9580 with your monitor's serial number to confirm your SST4's sensor slots.\u003c\/p\u003e\n\u003cp\u003eUnlike H2S, CO, and O2, there's no Limited-Life (2-year or 3-year alert-only) methanethiol monitor in the SST1 line to exclude from compatibility — the SST1-MM serviceable is the only methanethiol monitor in the WatchGas SST catalog.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003cdetails open\u003e\n\u003csummary\u003eWhy is the SST-SPARE-MM priced higher than the other RPL sensors?\u003c\/summary\u003e\n\u003cp\u003eThe SST-SPARE-MM is $300 — compared to $160 for the H2S, CO, O2, H2, and PH3 replacement sensors, and $180 for the SO2 sensor. Two reasons:\u003c\/p\u003e\n\u003col\u003e\n\u003cli\u003e\n\u003cstrong\u003eSpecialty cell chemistry.\u003c\/strong\u003e Methanethiol is a reactive sulfur compound. Building an electrochemical cell that responds accurately to CH4S without cross-sensitivity to H2S, dimethyl sulfide, dimethyl disulfide, and other structurally similar mercaptans present in Kraft mills, refineries, and wastewater digesters requires more specialized materials and manufacturing than a standard toxic-gas sensor. The unit cost reflects that.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLower-volume production.\u003c\/strong\u003e Methanethiol monitoring is a specialty need across the safety industry — many fewer sensors are produced per year than for H2S or CO. Lower volume means higher per-unit cost.\u003c\/li\u003e\n\u003c\/ol\u003e\n\u003cp\u003eCompared to a full new SST1-MM monitor at $460, the $300 sensor swap still saves you $160 (about 35% of the full-monitor price) — meaningful in a fleet context.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003cdetails open\u003e\n\u003csummary\u003eWhy is the SST-SPARE-MM warranty only 1 year (vs 2 years on other RPL sensors)?\u003c\/summary\u003e\n\u003cp\u003eMercaptan-tolerant electrochemical cells have shorter useful life across the safety industry — not a WatchGas defect. The cell chemistry is more susceptible to drift and cross-sensitivity because sulfur-containing compounds are chemically reactive and the sensor is designed to detect them without over-responding to similar sulfur species.\u003c\/p\u003e\n\u003cp\u003eFactor the 1-year warranty into your fleet's replacement cadence. For continuous-methanethiol environments (odorization plants, Kraft mills, biosolids digesters), a 12-month proactive replacement schedule is a reasonable default; less-continuous exposure environments may run the sensor 12–18 months and calibrate frequently.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003cdetails open\u003e\n\u003csummary\u003eCan I detect methanethiol by smell instead of relying on the sensor?\u003c\/summary\u003e\n\u003cp\u003eMethanethiol is one of the most-smellable gases in industrial hygiene — detectable at parts per billion, far below both OSHA's 10 ppm ceiling and NIOSH's 0.5 ppm ceiling. So workers absolutely CAN smell it before the exposure limit. But there are three practical problems with relying on smell:\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003e1. Olfactory fatigue.\u003c\/strong\u003e Mercaptans are one of the gases most likely to cause the nose to adapt within minutes. A worker who smelled it strongly on entry may not notice continued exposure 20 minutes later.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003e2. Odorant misattribution.\u003c\/strong\u003e Methanethiol is added to natural gas as a safety odorant. Workers in natural-gas-adjacent environments may perceive a methanethiol smell as \"a natural gas leak somewhere\" rather than a specific methanethiol exposure they need to measure.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003e3. Ceiling-limit dynamics.\u003c\/strong\u003e Both OSHA and NIOSH set CEILING limits for methanethiol (not TWAs). That means exposure at the limit is a compliance failure the instant it happens — not something you average across an 8-hour shift. A monitor gives you the ppm reading; smell doesn't.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003cdetails open\u003e\n\u003csummary\u003eCan I install the SST-SPARE-MM myself, or do I need to send the monitor to PK Safety?\u003c\/summary\u003e\n\u003cp\u003eBoth paths work. The SST1 platform is designed for user sensor replacement — the sensor cell is accessed through the monitor's service compartment, and the WatchGas SST1 manual walks through the swap procedure. After installation, you'll need to complete a full calibration to verify the new sensor's response against a known methanethiol standard.\u003c\/p\u003e\n\u003cp\u003eMethanethiol cal gas is a specialty item — corrosive, reactive, and typically not held on-site outside of specialty-gas-monitoring facilities. If you don't have methanethiol cal gas in your calibration workflow, sending the monitor to PK Safety for the swap and calibration verification is often the more practical path. We stock the appropriate cal gas and can verify the sensor's response before returning the monitor to service.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003cdetails open\u003e\n\u003csummary\u003eShould I replace the sensor or buy a new SST1-MM monitor?\u003c\/summary\u003e\n\u003cp\u003eThe SST-SPARE-MM sensor cell costs $300. A full new \u003ca href=\"https:\/\/pksafety.com\/products\/watchgas-sst1-serviceable-ch4s-gas-detector-sst1-mm\"\u003eSST1-MM monitor\u003c\/a\u003e costs $460. Sensor swap saves you $160 — about 35% of the full-monitor price for the maintenance action.\u003c\/p\u003e\n\u003cp\u003eThe sensor replacement is the more cost-effective path when your monitor's housing, display, battery, and electronics are in good working order. Full-monitor replacement makes more sense when the monitor itself is aging, has physical damage, or has a battery no longer holding charge — and a full new monitor also comes with the 3-year instrument warranty on the electronics (not just the sensor).\u003c\/p\u003e\n\u003cp\u003eCall PK Safety at 800.829.9580 with your monitor's condition and use pattern (continuous vs. intermittent methanethiol environment) and we'll walk you through the choice.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003cp\u003e\u003cstrong\u003eNot sure whether your SST4 has a CH4S sensor slot, or whether a sensor swap or full monitor replacement is the right path? Call PK Safety at 800.829.9580.\u003c\/strong\u003e A person who knows methanethiol monitoring and the SST platform's service ecosystem will pick up.\u003c\/p\u003e","brand":"WatchGas","offers":[{"title":"Default Title","offer_id":52671728320879,"sku":"WG01-SST-SPARE-MM","price":300.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0872\/5469\/6254\/files\/ES1-CH4S-800x800compressed.jpg?v=1771008669","url":"https:\/\/pksafety.com\/products\/watchgas-sst1-replacement-ch4s-sensor-sst-spare-mm","provider":"PK Safety Supply","version":"1.0","type":"link"}