The SO-421 has a fast response time of 14 seconds, is designed for use in lab applications, and has high-quality cable terminating in pre-tinned pigtail leads for easy connection to dataloggers and controllers. It comes with a thermistor temperature sensor to correct for temperature changes and a resistive heater to raise the temperature of the membrane approximately two degrees above ambient temperature to keep condensation from occurring on the Teflon membrane and blocking the diffusion path of the sensor. Typical applications include measurement of O2 in laboratory experiments, monitoring gaseous O2 in indoor environments for climate control, monitoring of O2 levels in compost piles and mine sailings, monitoring redox potential in soils, and determination of respiration rates through measurement of O2 consumption in sealed chambers or measurement of O2 gradients in soil/porous media.