Since 1991, EcoChem has pioneered the development and use of continuous real-time measurements of carbon aerosols using the Photoelectric Aerosol Sensor (PAS) technology. We offer different versions of this technology -- a handheld instrument for personal exposure and a standard desktop analyzer that can be configured for ambient air applications and source monitoring (with an appropriate sampling system). The Companion Products sections discusses the synergy between our PAS and Particle monitors. Extensive technical references are provided to illustrate the application of this technology world-wide.