Honeywell Gas Alert MicroClip XL and Honeywell GasAlert Max XT II - 4 Gas Monitors Explained

Honeywell Gas Alert MicroClip XL and Honeywell GasAlert Max XT II  -  4 Gas Monitors Explained
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Honeywell Gas Alert MicroClip XL and Honeywell GasAlert Max XT II - 4 Gas Monitors Explained

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Comparing the Honeywell GasAlert MicroClip XL and the Honeywell GasAlert Max XT II, it’s not hard to find the difference between these two 4 Gas Monitors, because there is only one. The XT II has an internal sample draw pump pre-tests and can be used as a continuous use diffusion monitor. The Micro XL can only be used as a diffusion monitor (no pump). Class dismissed if you’re here to find the differences between these two monitors. But, if you are interested in learning more about terms like "sample draw pump" or "pre-test", you should stick around.


Both monitors are 4 gas monitors, but that is an oversimplification. These monitors are versatile and can be used on worksites with a wide range of atmospheric conditions. At their root, they detect four main atmospheric hazards with the option to adjust individual settings as needed.

The main four hazards are hydrogen sulfide (H2S), carbon monoxide (CO), oxygen (deficiency and enrichment), and combustibles. The monitors keep track of these hazards with time-weighted averages short-term exposure limits and have the option of creating high/low setpoints.

In its simplest terms, time-weight averages (TWA) is a system that tracks toxic gas levels throughout your entire workday.

In more specific terms, OSHA limits the total amount of toxic atmosphere a worker can be exposed in one workday. The alarms on the monitors will trigger if the data collected exceed the acceptable threshold. These monitors take a reading every minute and plug that data in to get a cumulative average reading as the workday progresses.

The short-term exposure limit (STEL) is different. Instead of a cumulative number, STEL creates a rolling 15-minute average. Every minute, the monitors begin calculating a new average. If you turn on the monitor at 9:00am, the first average will be from 9:00am – 9:15am, the second average will be 9:01am – 9:16am, etc. If this data exceeds the set threshold, the monitor alarms will be triggered.

Both monitors utilize 4 sensors; oxygen, lower-level explosive limit (LEL), hydrogen sulfide, and carbon monoxide. The oxygen sensor is full-sized, and the other 3 are microsensors. All of the sensors are high quality and should last years.

Both monitors have three alarms: visual, audio, and vibration. When the monitor alarms are triggered, ALL three alarms will go off. The front of the monitors features three large lightbars that flash red at different speeds depending on the alarm. The monitors' speakers will emit a pulsed beeping alarm at 95 dB+ with varying speeds, again, depending on the alarm. The entire unit will vibrate.

This three-alarm system is highly effective because specific work hazards may require workers to clip the monitors in different areas. Hydrogen sulfide is a low-sitting gas. Workers may attach the monitor someplace low like their belt or on a leg pocket to get a faster reading. In that case, they may not be able to hear the monitor, but they should see the lights and feel the vibration.


Anytime you are in a confined space, you need a gas monitor. It doesn't matter if you are working, passing through, conducting an inspection, or you are an emergency responder. High concentrations of toxic gases will immobilize you hard and fast. Having a gas monitor allows you to quickly identify the hazard and get out.

A confined space is any space that is large enough for a person to enter/work in but is not large enough for a person to occupy for extended periods. Confined spaces have limited entry points and little to no ventilation. The different shapes, sizes, and entry points of confined spaces pose unique hazards. Some examples of confined spaces include storage tanks, silos, boilers, sewers, tunnels, buried utility vaults, pipelines, storm drains, and process vessels.

OSHA requires permits for hazardous confined spaces. If the space currently has a hazardous atmosphere or the potential of a hazardous atmosphere, a permit is required. Other conditions requiring a permit include whether the space contains flammable or toxic materials and if the walls, floors, or ceiling are sloping. Specified permits and other requirements are detailed in OSHA 29 CFR Part 1926.


As mentioned previously, the Honeywell Gas Alert Max XT II key feature is the sample draw pump. This unit can pull air in through the included hose directly to the sensors for testing. This is an important feature and should be used to test the air in a confined space before entering. This monitor is more expensive, but you only need one for an entire crew. The rest of the crew can wear diffusion monitors like Honeywell Gas Alert MicroClip XL.

On a side note, the XT II also doubles as a clip-on diffusion monitor. Removing the front plate shuts off the pump automatically and switches the unit to diffusion mode. Putting the plate back on switches the pump back on.

Pre-testing a confined space must be done correctly, and you’ll find that a large percentage of workers are doing it incorrectly. You cannot simply turn the monitor on, drop the hose in and pull it out a few seconds later. The sensors need time to get an accurate reading, and the pumps need time to pull air through the length of the hose. The longer the hose, the longer this test will take. Always refer to your monitors manual and manufacturer information. An industry rule of thumb is that it takes 2-3 seconds per foot of hose to get air to the sensors, and then it takes the sensors a minimum of 30 seconds to get an accurate reading.

Also, different gasses sit at different levels. Dropping a hose all the way to the bottom of a confined space will test for low-sitting gases but won't pick up on any of the higher gases. OSHA says tests should be conducted every 4ft. For example, if you are pre-testing a 10ft deep space using the included 10ft hose, you’ll need to test three different levels. Completing this test should take a minimum of 3 minutes. That's 1 minute per test (30 seconds for the air through the hose + 30 seconds for a sensor reading), conducted 3 times (ground, middle, top). If you are done testing in a matter of seconds, you have done the test incorrectly.


We’ve been asked why workers are required to wear a diffusion monitor if they’ve already conducted a pre-entry test. The atmospheric conditions in a confined space can change very quickly, and it’s directly affected by the work that you are doing. The air can quickly become toxic if you are degreasing, painting, welding, etc. The air can also rapidly change if you use a ventilation system that malfunctions or becomes contaminated. This can quickly happen if an unknowing vehicle idles by the ventilation inlet. A high concentration of carbon monoxide would be pumped into the confined space.


Having seen both types of monitors come in for service, I'd go out on a limb and say most workers aren’t cleaning these monitors. Cleaning 4 gas monitors is not required for them to function correctly. Given the pandemic, owners may decide to disinfect monitors before and after use. It is essential to know that alcohol-based cleaners and wipes will ruin the sensors. You also cannot use silicone-based cleaners, bleach, or dish soap. Honeywell recommended that these monitors be cleaned with mild soap and water and a damp cloth.


It is critical to power up the monitor in a clean air environment. Otherwise, it will not accurately read. It's important to understand that these monitors zero out when you power them up. The monitors can input values to manually zero out if needed. These monitors should be bump tested before each day of use. To conduct a bump test, you will need a tank of calibration gas and the testing clip and hose attachment for your unit. You connect the gas tank and expose the sensors. If the monitor is in working order, the alarms should trigger.

Calibration Check

This is more technical than a bump test. The sensors are exposed to specific gas concentrations to ensure the alarms are triggered at the intended levels. Calibrations are conducted in a certified lab and should be done every 180 days. PowerPak offers in-house calibration services that we cover in the video below. You can also find the calibration gas tanks, replacement parts, sensors, and accessories for these monitors in the PowerPak Gas Detection shop.


You can find both 4 gas monitors at, as well as more economical single gas monitors. We also offer a premium kit for the XT II that includes a calibration gas tank, a sampling prob, and other accessories.

Monitor owners within PowerPak’s delivery range can take advantage of our Gas Monitor Service. We will come to you, pick up your monitor(s), replace needed parts, conduct repairs, and calibrate with certification and return the monitor(s) to you within 48 hours.


Both the Honeywell Gas Alert MicroClip XL and the Honeywell Gas Alert Max XT II are reliable monitors used worldwide to keep workers safe. Still, these monitors are only as good as their users. Improper use of these monitors or ignoring/silencing the alarms put you and other workers at risk of long-term health issues or death. Be sure to use your monitors correctly and use them often.