Nitrogen dioxide (NO2) monitors are portable desktop instrument, which includes an internal pump. Nitrogen Dioxide concentrations in air can be measured with a resolution of 0.1 ppm and a range 0-20 ppm. The LCD display updates the concentration every 10 seconds. It also computes a 15-minute average and a time-weighted average. The internal pump can be combined with an extendable probe, to make it possible to sample from hard to reach areas or confined spaces.