Gas Monitoring in Wastewater Operations

Gas monitors can sometimes be a divisive subject in the safety world. The initial cost of implementing a comprehensive gas monitoring program can be a real barrier; then you must consider the time spent training users on the monitors, applicable software, docking station procedures, bump tests, repairs, and calibration schedules! However, the single most important thing to think about when considering a gas monitoring program is the lives that it can save! The nature of gases makes them inherently dangerous; many are colorless and odorless and by the time you might notice something is wrong, it’s already too late. Verona Safety is an expert in gas monitors from many manufactures and this is just a small guide to help you improve your program!

Some questions to consider when evaluating potential gas monitors for your program:

1. What gases do you need to monitor?

2. What environment are the monitors going to be used?

3. Do you need a diffusion or pumped monitor?

4. How many users do you have?

5. How many gas monitors do you need?

6. Is it worth it to buy the docking station, calibration gas and kit, or send it out for calibration?

7. How much data do you need?

A quick rundown of “bump testing” vs. “calibration”

A bump test checks the functionality of your gas monitor. This is a simple test that must be done prior to using any gas monitor. Bump test gas is cheap and readily available, and the test simply requires the user to turn on the monitor and blow gas over the sensors (aka “bump” the sensors with gas) in order to make the alarm(s) go off. This is a quick and easy test to ensure you are not going into the field with a defective monitor!

A calibration checks the accuracy of your gas monitor. This requires a bit more equipment and know-how, but is actually very easy to do! Here is the most common equipment required for calibration: gas regulator, calibration gas cylinder, and tubing. The manufacturer will state in the instruction manual what calibration gas mixture must be used and the procedure to follow. Calibration simply “resets” the sensors to the correct sensitivity, making the monitor accurate again. Additionally, calibration procedures often include automatic diagnostics that can tell you if a sensor is bad and need to be replaced!

Should you calibrate yourself or send your monitors in for service? This all depends on how much you want to do yourself, and how much time you have to manage your gas monitoring program. Calibrating is a relatively quick and easy process to learn, but does require some equipment and continued purchase of calibration gas. Most manufacturers require calibration of their monitors every 180 days, and certain units require calibration every 30 days. Over the long run, performing your own calibrations can save you money, but can also be very time-consuming. If you would rather have someone else handle this for you, Verona Safety offers in-house calibration service for most gas monitors.

Single gas vs Multi-gas monitors

Single gas monitors are often disposable, require no calibration, and no chargers; this makes them very economical and convenient. However, single gas monitors also include very few (if any) technological features that are becoming the standard today, such as data logging, inter-communication, man-down sensors, etc. Therefore, single gas monitors are best reserved for simple situations or short-term jobs that only have a single gas hazard.

Multi-gas monitors (specifically the standard 4-gas: CO, H2S, O2, LEL) are the golden standard used in today’s workplaces. The ability to be used in a wide array of applications, as well as the relatively economical price make them the most common gas monitor you will see in the field. Multi-gas monitors come in a wide range of styles with varied features but will commonly include more advanced technology such as datalogging. Additionally, multi-gas monitors often use rechargeable batteries and need to be charged prior to use.

You might also be aware of new disposable 4 gas monitors out on the market. These are becoming more popular because they combine the features and versatility of a multi-gas monitor, with the ease and convenience of a disposable monitor. These monitors usually are good for 2 years, require no calibration or charging, but after the time is up, they essentially become a paperweight! While these are convenient, the cost associated with replacing a fleet of monitors every couple of years can be a barrier for some.

Sensor Technology

When we are talking about what type of sensor a gas monitor uses, we are almost always talking about the LEL sensor. There are 2 types that you will find in a gas monitor: pellistor and IR. The pellistor sensor is older technology that uses a heating coil to burn the combustible gases present in the atmosphere in order to detect them. The newer IR sensor uses infrared light and how it is affected by the atmosphere, then it compares that to a reference point to show whether combustible gases are in the atmosphere. Pellistor sensors have 2 main downsides. First, because they use a controlled burn, they need oxygen in the atmosphere to operate. Therefore, they are not effective in atmosphere with low/no oxygen. Second, they can become “poisoned’ if they are subjected to prolonged and/or gas high concentrations, causing inaccurate readings. IR sensors suffer neither of the pellistor drawbacks, but do not work very well in environments with hydrogen or acetylene exposure risks due to the structure of these gases not being easily detected by infrared light. Additionally, IR sensors use much less power than pellistor sensors, leading to longer battery life. IR sensors, however, are not recommended in wet environments.

Diffusion vs Pumped and Confined Space

Another variant of monitor in today’s market is the pumped gas monitor. The standard gas monitors that you see in the filed with 3, 4 or 5 circular sensors are what is technically called diffusion monitors, as the gas diffuses across the membrane into the sensors. A pumped gas monitor works differently by adding a pump that actively pulls in the atmosphere and pushes it into the sensors. The most common application for the pumped unit is confined spaces. A pump with a tube and/or sampling rod can allows you to check what is in an atmosphere prior to sending anyone in to work. Additionally, there are 2 main types of pumped monitors, monitors with built in pumps, or monitors that accept a manufactures add-on pump. Monitors with built in pumps tend to larger, have poor battery life, and are purpose built, so they are not very versatile. Monitors that are made to work with a separate add-on pump are more versatile and allow for a single solution.

Not all gas monitor sales and service distributors are alike, make sure you qualify before you buy. With an emphasis on safety and a consultative approach to sales, Verona Safety is a company you can rely on!

Written and Submitted by Verona Safety, Madison WI. 608-273-3520