As energy, construction and industrial activities are increasingly present within colder climates, seasonal temperatures can make user conditions nothing short of extreme. Questions related to proper use and performance of portable gas detectors within cold temperatures arise frequently among users and those responsible for safety programs. While older detection technologies may have suffered from sensor signal shifts brought about by large downward temperature swings, modern gas detectors have become much more robust. Sophisticated real-time temperature compensation results in improved sensor readings and detector performance across a wider range of environmental conditions.
Electrochemical Sensor Performance
Chemical reactions are temperature-dependent, meaning that at lower temperatures, the rate of reaction decreases. Temperatures can affect sensor response in one of two ways:
- Transient Temperature – Temperature transients are significant temperature changes that occur within relatively short time periods, such as walking from a heated indoor office to wintery outdoor conditions. These rapid changes can cause temporary sensor shift, but that shift will stabilize when the sensor has completely cooled or heated to ambient conditions. Many MSA XCell® Sensors have an onboard, temperature sensor that helps to mitigate rapid temperature change effects.
- Steady State Temperature – When a sensor has completely acclimated to match that of the surrounding air temperature, the sensor is considered to be in a steady state. In this condition, the rate of reaction is stable and sensor output is steady
Temperature Compensation – For electrochemical sensors such as XCell O2 Sensors and other toxic gas sensors, the rate of reaction principle highlights the importance of temperature compensation for stable sensor output to improve performance while within both steady state and transient temperature changes. With MSA XCell Sensor technology, each sensor is manufactured with an ASIC (Application Specific Integrated Circuit) that controls sensor functions, digitizes sensor output to reduce electrical interference and may provide vital sensor-specific temperature compensation.
Electrolyte Freezing Point – Electrochemical sensors typically rely upon liquid electrolyte to support the sensing chemical reaction. Historically, sensors have relied upon a formulation to freeze at typically –28° C (–18° F). MSA XCell Sensors however, use a different formulation that allows sensors to continue to perform when temperatures drop as low as –45° C (–49° F).
In addition to sensor chemistry, other components can be susceptible to extreme temperatures.
Battery Performance – The rate of reaction principle also applies to an instrument’s power system: the battery. As alkaline batteries can easily lose 90% of capacity or more at cold temperatures, MSA ALTAIR Detectors use lithium-based battery technology that provides much improved cold weather performance over traditional battery chemistries such as NiCd, alkaline and NiMh technologies.
In addition to battery depletion, charging rate and depth can be affected by temperature effects. It is recommended that rechargeable instruments such as ALTAIR 4X, 4XR and 5X Detectors be allowed to warm up at room temperature for one hour prior to charging. Although charging at extremely low temperatures can damage certain batteries, MSA instruments are designed with thermal protection circuits that prevent charging from occurring at extreme temperatures.