Smart Sensor ST8904 4-in-1 Gas Monitor – O₂, CO, H₂S & LEL, Sound/Light/Vibration Alarm

The Smart Sensor ST8904 is a compact handheld 4-in-1 gas monitor for ambient checks of oxygen (O₂), carbon monoxide (CO), hydrogen sulfide (H₂S) and combustible gas (LEL). The English LCD shows all four channels at once with a SCAN status, while sound, light and vibration alarms trigger when a reading crosses your set thresholds.

Blue ABS shell with four front sensor windows, up/down/enter and power keys, and a top flash bar for visual alerts. Powered by a built-in BL-9C 3.7 V / 1800 mAh Li-ion pack charged over Micro USB (DC 5 V). Optional external sampling pump (sold separately) can be used for closed spaces per the maker’s guidance.

Key features

• 4-in-1 monitoring: O₂, CO, H₂S and LEL on one English backlit LCD
• Ranges: O₂ 0–30 %VOL · CO 0–999 ppm · H₂S 0–500 ppm · LEL 0–100 %LEL
• Triple alarm: sound + flash light bar + vibration; high/low settable; TWA / STEL (listing)
• Electrochemical sensors with continuous ambient scan
• Rechargeable BL-9C 3.7 V / 1800 mAh · Micro USB DC 5 V · ~6 h runtime (no alarm, listing)
• Pocket size: 140 × 75 × 35 mm · ~270 g body · blue shell with bumper

Specifications

• Model: ST8904
• Brand: Smart Sensor
• Gases: O₂ / CO / H₂S / LEL (combustible)
• O₂: 0–30 %VOL (0.1 %VOL)
• CO: 0–999 ppm (1 ppm)
• H₂S: 0–500 ppm (1 ppm)
• LEL: 0–100 %LEL (1 %LEL)
• Alarm: Sound / light / vibration
• Power: BL-9C 3.7 V / 1800 mAh Li-ion · Micro USB DC 5 V
• Runtime (listing): ~6 hours (no alarm)
• Operating range: −10 °C to 50 °C · 15–95 %RH
• Size / weight: 140 × 75 × 35 mm · approx. 270 g

Note: This listing is the Smart Sensor ST8904 4-in-1 gas monitor only (SKU EKO-ST8904). It is not the ST9700 single-gas CO alarm, AS8803 / AS8805 / AS8806, AR8100 / AR8200, AR8800A+, or any other sibling gas instrument—do not mix them. This is a portable ambient multi-gas monitor for trained users; it is not a fixed household carbon-monoxide alarm and is not offered as a certified life-safety system. Keep sensor windows clean; charge and service only in a safe area; follow the manual and local health & safety rules. If you smell gas or suspect a leak, leave the area and call the emergency gas line.

Free UK delivery. Dispatched in 1–2 working days, delivered in 5–7 working days. Price incl. VAT, VAT invoices available.

FAQ

Is this the ST9700 / AS8803 / AR8100 / AR8800A+?

No. This SKU is the ST8904 4-in-1 O₂/CO/H₂S/LEL monitor only (EKO-ST8904). Those sibling single-gas or gooseneck detectors are separate products and are not merged on this page.

Which gases does the ST8904 measure?

Four channels at once: oxygen (O₂ 0–30 %VOL), carbon monoxide (CO 0–999 ppm), hydrogen sulfide (H₂S 0–500 ppm) and combustible gas as LEL (0–100 %LEL).

Does it have sound, light and vibration alarms?

Yes. Triple alarm (sound + flash + vibration) when a channel hits the set high/low level. TWA and STEL alarm settings are supported per the listing/manual.

What battery and charge port?

Built-in BL-9C 3.7 V / 1800 mAh Li-ion, charged over Micro USB DC 5 V. Listing runtime is about 6 hours with no alarm active.

Is this a certified fixed life-safety / household CO alarm?

No. It is a portable handheld multi-gas monitor for ambient checks by trained users. It is not a fixed domestic CO alarm and is not sold as a certified life-safety system. Follow the manual and local regulations.

Is UK delivery free?

Free UK delivery. Dispatched in 1–2 working days, delivered in 5–7 working days. Price incl. VAT, VAT invoices available.