The DustTrak™ Environmental Monitor 8540 is a data-logging, light-scattering laser photometer that gives you real-time aerosol mass readings. It uses a sheath air system that isolates the aerosol in the optics chamber to keep the optics clean for improved reliability and low maintenance. It is designed for harsh outdoor settings, as well as harsh industrial workplaces, construction and environmental sites, and other outdoor applications. The robust design has an enhanced optics module, built-in auto-zero capability, and a longer life pump (>10,000 hours) which is field replaceable. The photometer measures aerosol contaminants such as dust, smoke, fumes and mists in environments from -4 to 122°F.* *Requires internal heater option.