I have been working in the gas detection industry for the past five years, and one of the questions I always get is, “Do I need a four-gas monitor?” Is a four-gas monitor a necessity, or is it optional?
In this post, I will analyze the 4-gas monitors when they are necessary, the gases they usually detect, and where they can be used.
I will also recommend the four best gas detectors on the market today.
What is a 4-gas monitor?
A 4-gas monitor is a gas detector intended to detect multiple gas concentrations simultaneously. It is one of the common monitors used in confined spaces.
What does a 4-gas monitor detect?
Using a four-gas monitor can protect your workers in any environment by assessing the four main gases: oxygen (O2), Carbon Monoxide (CO), Hydrogen Sulfide (H2S), Methane (CH4), or other combustible gases you’re checking for.
Oxygen (02)
Can be naturally depleted by stagnant air and oxidation of ores. Dead-end drifts, shafts, and any other opening with no airflow can have oxygen-deficient atmospheres.
Oxygen is generally displaced by carbon dioxide and nitrogen, so you don’t need separate sensors for those gases.
Methane (CH4), Other Combustible Gases
In most confined spaces, there is a danger of the presence of Methane and other combustible gases, this is measured in %LEL.
Carbon Monoxide (CO)
Carbon monoxide is a poisonous gas that is produced when fuels like oil, coal, wood, or gas don’t burn completely.
Hydrogen Sulfide (H2S)
You can smell Hydrogen Sulphide. However, extremely high hydrogen sulfide can quickly overload your sense of smell and you won’t notice it anymore. H2S isn’t a common gas in most abandoned mines, but it does occur.
Is a 4-gas monitor a necessity?
Depending on your application, a 4-gas monitor can become a necessity or not, there are some environments where OSHA mandates using 4-gas monitors.
Confined spaces
These spaces are inherently dangerous and can pose a safety risk. 4-gas monitors are often required during entry into confined spaces and may be a permanent fixture in some spaces.
Attics and crawl spaces
Tradespeople who work in attics and crawl spaces regularly may need to use a 4-gas monitor.
Water and wastewater treatment
4-gas monitors are often used in water and wastewater treatment facilities.
Mining
Mining operations can pose a risk of exposure to methane, hydrogen sulfide, and carbon monoxide.
Scientific and medical environments
Technicians in life science and incubation environments may need to use 4-gas monitors to analyze oxygen and carbon dioxide levels.
Pros and Cons of using a four-gas monitor
Pros of using a four-gas monitor
- Ensure maximum safety and protection from several gases
- Easily detect hazardous gases in one device
- Audible/Visual instant indication should hazardous levels be present
- Portable, hand-held, and battery-operated options so you can monitor quickly from place to place
- Data logging capabilities to monitor concentrations over time (portable options).
Cons of using a four-gas monitor
- Routine calibration and testing is required for accurate performance
- Some gas detectors only last 2-5 years, depending on the gas sensor
- Can not monitor every hazardous gas in one platform
What is a 4-gas monitor in a confined space?
A 4-gas monitor is a confined space that should be able to prevent risks linked to low oxygen atmospheres, toxic gas or vapor presence (like carbon monoxide or hydrogen sulfide), or even explosive and combustible atmospheres (like hydrocarbons, solvents, or alcohols).
How long does a four-gas monitor last?
The typical lifespan of any gas detector depends on the type of sensor technology used at its core, the environment, and how well you maintain your monitor.
For reference, most electrochemical sensors last 2-3 years, and non-dispersive infrared sensors last 5-15 years.
How often should you calibrate a four-gas monitor?
The calibration frequency for a four-gas monitor, or any gas monitor, depends on several factors, including manufacturer recommendations, specific industry requirements, local regulatory requirements, usage conditions, and the specific gas sensors involved.
Before calibration your four-gas monitor, I recommend consulting the manufacturer’s guidelines and manuals for the specific gas monitor model you are using, as they will provide the most accurate and reliable information.
Most gas detector manufacturers recommend calibrating the units at least once a year.
I recommend checking the manufacturer guide and local regulations and adjusting the calibration frequency accordingly.
What are the typical four gas meter alarm levels?
Provided standards exist, all alarm settings are based on the following OSHA PEL, TWA, and STEL settings.
| GAS | LOW | HIGH | TWA | STEL |
| Oxygen (O2) | 19.5% vol | 23.5% vol | N/A | N/A |
| Carbon Monoxide (CO) | 25 ppm | 100 | 25 ppm | 200 ppm |
| LEL | 10%LEL | 20%LEL | N/A | N/A |
| Hydrogen Sulfide (H2S) | 10 ppm | 20 ppm | 10 ppm | 15 ppm |
How do you select a multi-gas detector?
When selecting your four gas monitors, you must ask yourself a few questions; here are the factors to consider.
What gases do you want to detect?
Some four-gas monitors come with all four sensors; most four-gas monitors come with CO, O2, H2S, and a combustible sensor (LEL).
If those are the gases you want to detect, you can select one of those monitors.
Do you want a pump?
Some of the four gas monitors, like the MAX XT II, have a built-in pump, which is great for applications that require sampling or confined space.
Other four gas monitors, like the Microclio XL, do not have a pump, which is useful in applications where you do not need to draw the gas toward the pump; the gas will diffuse into the unit.
How to Select the Right Gas Detection Solution
FAQ: Four Gas Monitor
What is the best four-gas monitor?
Max XT II is the best 4-gas monitor. GasAlert Max XT II is the smart, simple, economical way to comply.
Workers feel safe, and incidents are minimized so everyone can do more. That means savings realized from business continuity and productivity.
What is the best maintenance-free four-gas monitor?
BW Clip4. The BW Clip4 is a low-cost way to enjoy high-quality protection and comes with supporting technologies of Honeywell quality.
Once you clip it on, it stays on. Activate and Forget about it. Just activate your BW Clip4, and it will stay on. You never change or charge the battery. This protection lasts for two full years.
What does an MSA 4 gas monitor detect?
ALTAIR 4, Multigas Detector for LEL, CO, H2S, and O2, raises the standard for personal multigas detectors by offering a combination of features you won’t find in competitive models.
Will a 4-gas monitor detect natural gas?
Four gas monitors with an LEL sensor detect natural gas. Natural gas is almost entirely methane, although it contains small amounts of other gases, such as ethane, propane, butane, and pentane.
How To Detect A Natural Gas Leak
How often should you calibrate a four-gas monitor?
Calibration is recommended annually if bump testing indicates an out-of-spec sensor. Due to the technology of electrochemical sensors, they will deplete over time and more rapidly if exposed to the target gas.
What is LEL on a four-gas monitor?
LEL stands for “Lower Explosive Limit” and is the lowest gas concentration that is potentially flammable or combustible.
In other words, the minimum amount of gas will catch fire or explode when an ignition source is present.
Will a four-gas monitor detect hydrogen?
The four-gas monitor containing LEL or combustible sensors will detect Hydrogen.
Does a four-gas monitor detect methane?
Any combustible gas (LEL) sensor in the four-gas monitor will detect methane.
Key Takeaways: 4-gas monitor
4-gas monitors can protect your workers in any environment by assessing the four main gases: oxygen (O2), Carbon Monoxide (CO), Hydrogen Sulfide (H2S), Methane (CH4), or other combustible gases you’re checking for.
For confined spaces, select a four-gas monitor with a built-in pump. Most manufacturers recommend calibrating the four-gas monitor at least once a year, but you should always check with local or industry-specific regulations for calibration frequency.