The Canary In Your Coal Mine

A lot of our daily work tasks require personal protective equipment (PPE) to get the job done safely. Different tasks require different PPE. An air monitor is one PPE often used while working in a confined space. Depending on where it is employed, it could save your life. Different types of air monitors detect different types of gas, so it is important to use the appropriate model for your situation. The typical 4-gas air monitor works well for the majority of confined spaces as long as nothing introduces an unexpected chemical like chlorine into the environment. The 4-gas air monitor detects oxygen, carbon monoxide, hydrogen sulfide, and the lower explosive limit. No matter what type of air monitor is used, these devices are constantly facing tremendous wear. They are deployed in tight working environments, exposed to gas and extreme temperatures, and are often thrown around. But, how can you tell if your air monitor is working properly? Is it because it turns on and doesn’t beep at you? Or is it because you have followed the manufacturer’s recommendations for use, handling, and maintenance?

To ensure your air monitors are taken care of, you will need to perform bump tests and calibration tests to evaluate its functionality and accuracy. The process for bump testing your air monitor varies depending on the type and model of air monitor you have. Refer to the manufacturer for how to bump test your device. The Occupational Safety and Health Administration (OSHA) defines a bump test as “a qualitative function check in which a challenge gas is passed over the sensor(s) at a concentration and exposure time sufficient to activate all alarm settings.” Basically, this means that the gas is acting as a potentially hazardous environment to be detected by the sensor.

Calibrating is essential in maintaining the accuracy of your sensor reading, which unfortunately, degrades over time. You will also need to take into account the manufacturer recommendations, which tend to vary. For example, RKI Instruments suggests a monthly calibration of their monitors. They also state that daily bump tests of their portable instruments is neither necessary nor entirely useful; the built-in diagnostic should be able to tell the user whether or not it is working properly. On the other hand, Mine Safety Appliances and BW Technologies both recommend bump testing before each use. We believe it’s in your best interest to do the bump test because it is still your first line of defense for identifying potential failures in confined spaces, which could easily become a life-and-death situation.

According to the OSHA Information Bulletin, the following are the potential failure modes that can be identified during a bump test.

1. Gradual chemical degradation of sensors and drift in electronic components that occur naturally, over time;
2. Chronic exposures to, and use in, extreme environmental conditions, such as high/low temperature and humidity, and high levels of airborne particulates;
3. Exposure to high (over-range) concentrations of the target gases and vapors;
4. Chronic or acute exposure of catalytic hot-bead LEL sensors to poisons and inhibitors. These include: volatile silicones, hydride gases, halogenated hydrocarbons, and sulfide gases;
5. Chronic or acute exposure of electrochemical toxic gas sensors to solvent vapors and highly corrosive gases;
6. Harsh storage and operating conditions, such as when an instrument is dropped onto a hard surface or submerged in liquid. Normal handling/jostling of the equipment can create enough vibration or shock over time to affect electronic components and circuitry.
7. In addition to aforementioned, any general component failure.

It should also be noted that paint, aerosols, mud and other debris will frequently block sensor inlets.
With today’s complex monitors, it may not seem like bump testing daily is necessary. However, you could find yourself in a number of situations that prove otherwise. For example, if an air monitor is used by multiple people throughout an organization, the last person to use it before you may have mishandled the equipment. There could be blocked sensors or faulty electronics because of the way it had been treated. Additionally, the European Committee for Electrotechnical Standardization, International Electrotechnical Commission, International Safety Equipment Association, and OSHA all recommend the best practice of a daily bump test for air monitors. Make sure you know the requirements of your specific air monitor and maintain it to the best of your ability. It could be the one PPE that saves your life when you are in a tight spot.

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