With the month of October comes the beginning of cold weather season in the northern hemisphere and concerns about how well your portable gas detection equipment will function when winter puts its death grip on the thermometer. Some instruments are rated as low as -40 degrees; however, the low temperature rating for continuous operation of most portable gas monitors is -20 degrees Celsius. Even so, most instruments may be used at lower temperatures for intermittent periods. Sensor response will certainly change as the temperatures get colder, but more sophisticated gas monitors typically use “temperature compensation” to keep gas readings within +/-15% of the actual concentrations.
Here are some tips to help you get a warm feeling when using gas detectors in cold weather.
1. When you walk outside, you feel the cold instantly. However, it will take a while for your gas monitor to reach equilibrium with the ambient temperature. The temperature compensation will typically track with the internal temperature of the monitor. If you are going to be using the monitor for 20 minutes or less, there is no reason to allow it to stabilize and adjust to the temperature before using it. Turn it on, take your readings and get back inside where it is warm.
2. If you will be using your monitor outside for extended periods longer than 20 minutes, it is best to let it stabilize at the ambient temperature for 15 – 20 minutes before use, and then turn it on and zero the sensors in fresh air.
3. Particularly in the Northern Plains, North West Canada, and Alaska, the cold winter climate is extremely dry. The dry climate has more impact on the performance of some electrochemical sensors than even the coldest of temperatures. To prevent the aqueous electrolytes from drying out, store and charge your instruments in a humidified area when not in use. Keeping the ambient relative humidity at forty to fifty percent will go a long way toward maintaining the sensitivity of your sensors and will keep them working longer.
4. The response of the instrument may appear to get sluggish at temperatures below -20C. The display may get dim and even go blank if it freezes. If this happens, your gas monitor will likely still detect gas and will still alarm. If you have to use it this way, you should bump test it before each use to make sure it responds, and you should get the instrument warmed up as soon as possible.
5. The electrochemical sensors in your instrument typically have an aqueous electrolyte, and in some cases, may freeze as temperatures drop below -20C for an extended period. The oxygen sensor will normally be the first to freeze. When frozen, the sensors will not be able to produce a reliable reading, but functionality should return once they warm up and thaw out.
6. Battery run time may be reduced in cold temperatures. Below -20C, run time may be reduced by 50% or more.
7. Keeping your gas monitor close to your body will keep it as warm as possible. If you are using the monitor for remote sampling, keeping it inside your coat as long as possible will help keep it warm and functioning longer.
A good rule of thumb for using gas detectors in cold weather is that your gas monitor can generally stand to be out and working in the cold as long as you can. If it’s too cold for you, it’s probably too cold for the instrument as well.
Baby it’s cold outside, so until the milder temperatures of spring return, work safe, and try to keep warm.