Table of Contents

Introduction

Carbon monoxide (CO) is the classic silent killer: colourless, odourless, tasteless and produced by the incomplete combustion of almost any carbon-based fuel. Unlike hydrogen sulfide, it gives no odour warning. A worker in a boiler house, a parking garage, a tanker deck or a petrochemical furnace duty can be overcome before they realise something is wrong. For EHS managers and plant engineers operating in Russia and the Middle East, a reliable CO gas detector is therefore not optional — it is the front line of both personal safety and regulatory compliance.

This guide explains how CO harms the body, which exposure limits apply, where CO hazards are most likely, how electrochemical CO sensors work, and how to choose between fixed and portable detection. It is written around the EAC (TR CU 012/2011), ATEX and IECEx frameworks that govern explosive-atmosphere equipment in Eurasian Union and Middle Eastern projects, rather than around US-only rules.

What Makes Carbon Monoxide So Dangerous

CO binds to haemoglobin roughly 200–250 times more strongly than oxygen, forming carboxyhaemoglobin (COHb) and starving the brain and heart of oxygen. Symptoms develop insidiously: headache and nausea at first, then dizziness, confusion and loss of consciousness. Because the early symptoms mimic ordinary fatigue, workers often stay on task until it is too late. CO is slightly lighter than air and mixes readily, so it does not always pool at floor level — detection must be placed at breathing height near the combustion source and at discharge points.

Exposure Limits: The Numbers That Set Your Alarms

Alarm set-points are derived from occupational exposure limits. The values below are the widely cited reference limits from NIOSH, OSHA and ACGIH; EAC and ATEX-certified equipment is calibrated to these same ppm ranges. Always confirm the current jurisdiction-specific limit with your approved EHS body, because national OEL tables are periodically updated.

Reference body	Limit	Value (CO)
OSHA PEL (29 CFR 1910.1000)	8-hour TWA	50 ppm
NIOSH REL	8-hour TWA / ceiling	35 ppm / 200 ppm
NIOSH IDLH	Immediately dangerous to life or health	1,200 ppm
ACGIH TLV	8-hour TWA	25 ppm

In practice, portable four-gas detectors such as the HD620 use a low CO alarm around 25–35 ppm and a high alarm at 100–200 ppm. Fixed system alarms are then interlocked with ventilation, isolation valves and site-wide alarms via the plant controller.

Where CO Hazards Appear in Industry

Boiler houses, furnaces and thermal oxidisers, including start-up and shutdown transients when combustion is unstable.
Petrochemical and refinery units: catalytic crackers, sulfur recovery and flared-gas handling, common across GCC and Russian refinery sites.
Parking garages, tunnel ventilation and vehicle-maintenance bays with diesel exhaust.
Confined spaces: tanks, vessels, sewers and silos where combustion or oxidation can deplete oxygen and generate CO.
Offshore and onshore drilling: diesel generators, mud-logging units and crew-quarter heating.
Seawater desalination and power-generation plants in the Middle East, where gas turbines and heat-recovery steam generators run continuously.

How Electrochemical CO Sensors Work

Almost every modern CO gas detector uses an electrochemical (fuel-cell) sensor. A controlled current is generated when CO crosses the sensor’s working electrode, and that current is proportional to CO concentration over a calibrated range (typically 0–1,000 ppm). Electrochemical sensors are selective, draw very little power and offer ppm-level accuracy — ideal both for portable personal monitors and fixed transmitters.

They are not perfect. They drift, they are poisoned by certain silicones and H2S, and they age — typical sensor life is two to three years. This is why daily bump testing and a full calibration at least every six months (more often in heavy-duty service) are mandatory. A sensor that has not been exposed to test gas cannot be assumed to respond.

Fixed vs Portable CO Detection

Continuous, unmanned process areas need fixed detection. A fixed CO detector such as the HD9300 mounts near a burner or flue-gas duct, transmits 4–20 mA / RS485 / MBUS signals straight into the DCS or PLC, and switches on dual alarms and ventilation relays automatically. With an Ex d IIC T6 Gb enclosure and operation from –40 °C to +70 °C, it suits the cold Russian winter and the hot Middle Eastern summer alike.

See the fixed detector: HD9300 3-Wire / 4-Wire Fixed Gas Detector with LCD Display

See the controller: HD6000 Fixed Gas Alarm Controller (2–128 channels)

Personal protection and confined-space entry need portable detection. Before anyone enters a boiler cellar, storage tank or vessel, the atmosphere must be tested with a pump aspirated instrument. The HD620 four-in-one pump detector measures CO alongside H2S, O2 and LEL on a 2.4-inch colour screen, is rated Ex ia IIC T4 Ga and IP65, runs about 20 hours on a 5,000 mAh battery, and combines audible, visual and vibration alarms with English and Chinese voice prompts.

See the portable detector: HD620 Four-In-One Pump Portable Gas Detector

Well-run facilities run both: fixed detectors watch process areas around the clock, while portables protect each worker and any entry into unknown atmospheres. A single-point wall-mounted controller such as the HD6100 can bring a small fixed point and a local alarm together in one enclosure for equipment rooms.

Hangwei CO Detection Solutions

Henan Hangwei Sensing Technology Co., Ltd. (Hangwei Sensors) has more than 20 years of manufacturing experience, holds 20 patents and operates 10 production lines. We supply fixed and portable CO gas detectors, controllers and custom sensor packages for EAC, ATEX and IECEx-oriented projects, and we support OEM/ODM and global distributor recruitment.

Fixed CO detection: HD9300 series, Ex d IIC T6 Gb, –40 to +70 °C, 4–20 mA / RS485 / MBUS to DCS/PLC, dual relays, IR remote calibration.
Portable CO detection: HD620 four-in-one (H2S/CO/O2/LEL), Ex ia IIC T4 Ga, IP65, ~20 h battery, pump or diffusion versions.
Controllers: HD6000 from 2 to 128 channels, 2/3/4-wire, LCD or colour display; HD6100 single-point all-in-one.
Custom packages: special ranges, mixed sensor configurations and detector-plus-controller systems built around your site layout.

Start a custom project: Custom Gas Sensor & Detector Solutions

FAQ

How quickly does carbon monoxide make a worker unconscious?

At low concentrations (50–100 ppm) symptoms build over hours; at 1,200 ppm — the NIOSH IDLH level — effects appear within minutes and escape without aid may be impossible. This is why continuous monitoring and personal alarms are essential.

Can I rely on my sense of smell to detect CO?

No. Carbon monoxide is completely odourless. Olfaction is never a detection method for CO; only calibrated instrumentation is reliable.

What alarm set-points should I use for CO?

A common starting point is a low alarm at 25–35 ppm (matching ACGIH/NIOSH TWA) and a high alarm at 100–200 ppm, with the highest alarm interlocked to ventilation and isolation. Final set-points must follow your local OEL and risk assessment.

Does a CO detector also measure other gases?

Not as a pure CO sensor. A four-gas portable such as the HD620 measures CO, H2S, oxygen and LEL simultaneously — the standard configuration for oil-and-gas and confined-space work.

How often must CO sensors be calibrated?

Bump test before each shift, and full calibration at least every six months, or sooner if the sensor fails a bump test, is dropped, or operates in a corrosive or high-dust environment.

Are these detectors suitable for explosive atmospheres in Russia and the Middle East?

Yes. The HD9300 fixed detector is Ex d IIC T6 Gb and the HD620 portable is Ex ia IIC T4 Ga; both can be supplied to support EAC (TR CU 012/2011), ATEX and IECEx project documentation.

Get Expert Guidance

Specifying a CO gas detector is a safety-critical decision. Hangwei Sensors designs and manufactures fixed, portable and controller-based CO monitoring systems for oil and gas, power, desalination and general industry across Russia, the Middle East and beyond. Contact our engineering team to discuss detector placement, alarm set-points, EAC/ATEX documentation and distributor or OEM terms.

Email: hw@hangweisensors.com | Phone: +86 371 6667 0886

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