We bought equipment from Envieq and were pleased with it. They have a wide range of photoionization detectors https://www.envieq.com/product-category/air-and-gas/photoionization-detectors/ from reliable brands, including RAE Systems and Ion Science, which work consistently in challenging environments and have excellent sensitivity even to low concentrations. In operation, the instruments proved to be reliable: fast response, user-friendly interface, housing withstands dirt and moisture. What is important - the delivery was calibrated, and Envieq's technical support really helps, not just replies with excuses.