Best 4 Gas Monitor for Confined Space (2024 update) (2024)

What Does 4 GasMonitor for Confined Space Measure?

A 4 gasmetermeasures carbon monoxide (CO), oxygen (O2), hydrogen sulfide (H2S), and combustibles (EX). The combustibles sensor is non-specific, meaning that it can detect a variety ofgases.Acetone, industrial solvents, alcohol, ammonia, lacquer, thinners, benzene, methane, butane, naphtha, ethylene oxide, natural gas, gasoline, propane, halon, refrigerants, hydrogen sulfide, and toluene are just some of the combustibles that a 4 gas monitor can detect.

What Does a 4 GasMeter Do?

The primary purpose of a 4 gas monitor is toalert users to any hazardous air quality environments. These instruments protect workers from unseen workplace gas hazards. 4 gas monitorswarn the users of any unsafe air quality environments through audible, visual, and vibration alarms.

What Are the Different Types of 4 Gas Monitors?

How Do 4 Gas Sensors Work?

A 4 gas monitoris composed of electronics andfour sensors. The gas sensors convert the detected gas concentration to an electronic signal for analysis by the on-boardmicroprocessor. From there, the processor outputs the reading to the display screen. If the readings exceed the pre-set alarm values, the alarms will be triggered to warn the user.

As the name suggests, there are four sensors used in a 4 gas monitor. The O2, H2S, and CO sensors are electrochemical cells. The combustibles sensorreading %LEL is most often recorded by a catalytic bead pellistor sensor.

Is Using a 4 Gas Monitor Mandatory?

In certain occupational situations, a 4 gas monitor is mandatory. Several OSHA standards require the use of multi-gas monitors.

• Permit-required confined spaces: paragraph (c)(5)(ii)(C) of 29 CFR 1910.146, see here.
• Hazardous waste operations and emergency response: paragraph (c)(6) of 29 CFR 1910.120 (Hazardous Waste Operations and Emergency Response), see here.
• Grain Handling Facilities: Section 5 (Entry Into Bins, Silos, and Tanks) in Appendix A of 29 CFR 1910.272, see here.

What Are Safe4 Gas Monitor Levels?

Various government agencies and associationsrecommend specificgas exposure limits. Below are some examples for each gas included in a typical 4 gas monitor.

Oxygen (O2) Deficiency

Carbon Monoxide (CO)

Hydrogen Sulfide(H2S)

Combustibles, Explosives (EX) %LEL (Methane)

Do4 Gas Detectors Indicate Which Gas Is Being Detected?

Yes. they do. Since there is an array of 4 sensors, they present the corresponding gas levels being detected. However, for the combustibles sensor, it cannot discriminate from the hundreds of different combustible gases that may be present. The majority of combustibles gas detectors are calibrated to methane. Therefore, the values presented during detection will bewith respect to methane.

What Is a 4 Gas Monitor Used For?

4 gas monitors are used for personal protection in hazardous gas environments where air quality may be compromised. Confined spaces can pose a safety risk, as highlighted below:

• Industrial Tank:A gas leak detector with a gooseneck is placed in a tank before the worker enters to sniff for any residual combustibles that may have accumulated. When the readings are within safe limits, the worker may enter the tank. They will also carry 4 gas detectors while in the tank to protect fromoxygen deficiency and combustible residue.
• Plumber/Electrician: Trade workers such as plumbers and electricianssometimes enter confined spaces. Closedspaces in residentialand building spaces often do not have proper ventilation, leading to a lack of fresh air. In this case, oxygen deficiency isa major concern and a 4 gas detector is an excellent choice for the worker.
• Wastewater/Sewerage:The wastewater industry keeps our sewers and sewerage systems working. When cleaning these areas,workers are oftenin confined places where biological breakdown may emit combustibles. Along with methane and hydrogen sulfide exposure,wastewater and seweragespaces may be oxygen deficient. Personal protection using a 4 gas monitor is a wise decision.
• Mining: Similar towastewater, mining also poses the risk of methane and hydrogen sulfide exposure. Carbon monoxide, a toxic gas, may also be present and oxygen levels may be depleted. In these situations, using a 4 gas monitor is asafety necessity.

Cana 4 Gas Monitor Be Used to Detect a Gas Leak?

No, we do not recommend using a 4 gas monitor for pinpointing suspected gas leaks in a pipe, joint, or appliance. A gas leak detector that employs a gooseneck, semiconducting metal oxide sensor, and ppm reading is the most desirable detector for this specific application.

How Do I Select a 4 Gas Monitor?

To select the best4 gas monitorthat serves your purpose, follow this guide. It is important to narrow down your selection by thinking about thesequestions:

• Do I need a built-in pump or probe with the unit?
• How often will I use it? What battery capacity do I need?
• What is my budget and operating cost budget?
• Do I need advanced functions such as data-logging,bluetooth, or printing?
• Do I need specific accreditations with the monitor, such as ATEX or a NIST traceability calibration certificate?
• Do I require a belt clip for attaching onto my clothes?
• Is after sales support, USAheadquarters, or fast calibration service required?
• Does a standard 4 gas monitor meetmy application requirements? Or do I need to custom order a specific 4 gas monitor with other detected gases?

What Are 5 Gas and 6 Gas Monitors?

Similar to a 4 gas monitor, 5 gas and 6 gas monitors includes extra sensors in the hardware to detect additional gases. Below is a picture of a 6 gas monitor with built-in pump. This unit detects CO, H2S, EX, O2, CO2, and NO2.

How Long Do 4 Gas Monitor Sensors Last For?

4 gas monitors usingcatalytic bead sensors to detect combustibleswill usually work for over 5 years.Electrochemical cell technology sensors, used to detect O2, H2S, and CO, typicallylast between 24 to 36 months.

How Do I Test My 4 Gas Monitor?

The best way to test your4 gas monitor is toexpose it to a known gas source, typically multi-gasbump gas. Generally referred to as bump testing, this is good practice to perform daily, especially in personal protection applications.

What Is a 4 Gas Monitor Bump Test?

• Bump testing is a procedure when one exposes the gas detector to a small amount of “blast” target gas to ensure the detector operates and alarms as programmed.
• The function of this test is to verifyproper operation and build user confidence, particularly in hazardous applications.
• It is recommended to bump test when first purchased and follow with weekly checks. If using in LIFE THREATENING and/or DANGEROUS applications, bump test daily. See video explanationhere.

What Is 4 Gas Monitor Calibration?

4 Gas monitor calibration is the technical task of adjusting the detector to provide a more accurate gas reading. Because the sensors may degrade or drift over time, we typically suggest to calibrate your 4 gasmonitorbetween 6 to 12 months. This time period is typical for gas detectors.

Gas calibration is a technical task and requires certain key piecesofequipment. This includes a multi-gas calibration gas bottle, gas regulator, tubing, calibration cap fitting, and your 4 gas detector. You need to confirm with the manufacturer to determine the recommended calibration gas concentration levels and mixtures. For the Forensics Detectors 4 gas monitors, we recommend gas calibration with a mix of CO at 200 ppm, H2S at 25 ppm, O2 at 18%, and Methane at 50%LEL.

Be attentive and calibratedaily if:

• The user is employing the device as an analytical tool where accuracy is paramount.
• The user is using the device in an extreme environment (temp and humidity extremes create sensor drift).
• The user is undertaking an imminently dangerous or extreme application.
• Bump testing fails. In this case you must calibrate to make sure the sensors and monitor are able to alarm.
• The 4 gas detector is alarming in fresh air. This means that a sensor has potentially drifted pastan alarm set-point (the oxygen sensor tends to drift low).

Calibration and bump testing is mandatory because injury or death will occur if the device fails. Take it very seriously.

Also, it is prudent to have a calibration schedule that the owner or employees strictly follow.

How Do I Take Care of My 4 Gas Monitor?

• Store your 4 gas detector at a normal room temperature - about 70Fwith 50%RH (well within operating specifications).
• Store it away from electromagnetic or magnetic sources, such as phones.
• Store it in a clean environment where no dust or particles exist.
• Store it away from any exhaust gas, concentrated vapors, or harsh chemicals.
• Clean the casing of your detector with a damp cloth.
• Store it in a stable place where there are no vibrationsor continuous shaking.

How Do I Properly Use a 4 Gas Monitor?

When operating a4 gas monitor, there are some important tips to consider. Obviously, be smart and read your product manual. In addition, keep these tips in mind:

• Turn ON the 4 gas monitor in fresh air.
• Ensure the 4 gas monitor is within its calibration period.
• Ensure the 4 gas monitor has been bump tested and validated as operational. Ensure levels have come to baseline. CO, H2S and EX should read 0ppm and O2 should be around 20.9%.
• Check alarm set-points. Set your alarms as desired.
• If undertaking analytical measurements, keep the unit stationary. Ensure humidity and temperature are also tracked andare as constant as possible.
• If using a pump, turning the pump ON/OFF will change the pressure and may affect readings. Take data point readings when either the pump is off oron after 60 seconds so the "pressure change" does not createinaccurate readings.

What Is the Difference Between ppm and %volDetector Readings?

A typical 4 gasmeter presents oxygen readings as a percentage. The H2S and CO readings will bedisplayedin ppm. The combustibles will beshown as %LEL. It is important to know how these measurements are related.

The typical scale of concentration for any gas is%vol. The meanswhat % of the air volume is taken up by the gas volume. There are other measures based on weight and mols, but gas detection primarily involves readings on a volumetric basis.

The part per million (ppm) scale has a direct conversion from %vol. 10,000ppm = 1%. Both of these values are interchangeable. Once ppm values enter the thousands, it is customary to start using %vol. Fo example, it is easier to say 1.1 %vol instead of 11,000 ppm.

Conversion Example

Oxygen % value = (oxygen ppm / 1,000,000) x 100%

For example, if we have 5,000 ppm of oxygen, then we obtain:

Oxygen% value = (5,000 / 1,000,000) x 100%

Oxygen% value = 0.5%

Quick Conversion From ppm to %vol

100 ppm = 0.01%

1,000 ppm = 0.1%

10,000 ppm = 1%

100,000 ppm = 10%

1,000,000 ppm = 100%

What Is the Difference Between ppm and %LEL Detector Readings?

When your 4 gas monitor reads the combustible levels, ituses %LEL. This is different than ppm and %vol units.%LEL represents a percentage of the lower explosive limit of a particular combustible. This can be a bit tricky, butfollow along slowly to understand the difference:

Each combustible has a different explosive limit in air, and therefore a different lower explosive level (LEL).

For example, methanewillexplode in air at 5% volume (which is 50,000 ppm). This iscalled the 100% Lower Explosive Limit. In other words, 100% LEL = 5% volume. When methane concentration levels reach 100% LEL, the gas will explodeif an ignition source is present. For propane, 100% LEL = 2.1% volume, and for hydrogen, 100% LEL = 4.0% volume.

So the %LEL scale is based entirely on explosive limits. As you can imagine, each gas has different explosive limits.

Example: If our 4 gas detector is reading 5% LEL and it has been calibrated to methane, then 5% of [5%vol] = 0.25 %vol or 2500 ppm.

Final Words

4 gas monitors are essential gas detection devices that simultaneously measure the levels of carbon monoxide (CO), oxygen (O2), hydrogen sulfide (H2S), and combustibles (EX) in the air. These monitors are crucial for ensuring personal safety when working in confined spaces such as tanks, vessels, silos, pits, manholes, and tunnels, where hazardous gases can accumulate. When unsafe conditions are detected, 4 gas monitors alert users through a combination of audible, visual, and vibration alarms, allowing workers to take immediate action to protect themselves. These versatile devices are widely used across various industries, including maritime, oil and gas, construction, mining, water, and wastewater, where the presence of dangerous gases poses a significant risk to worker safety. To maintain the highest level of safety and ensure accurate multi-gas detector operation, it is essential to perform regular bump tests and calibrations on the 4 gas monitors. By adhering to these best practices, workers can rely on these life-saving devices to provide real-time, reliable gas detection in even the most challenging environments.