ABSTRACT
There has been increasing concern over airborne microparticles in the environment and the potential health risks they produce (Nobel and Prather, 1998; Holgate et al., 1999). Detection of such particles in real-world conditions has traditionally been done with laser light scattering using optical particle counters (OPCs) (Welker, 2012). However, the use of free space laser beams can be restrictive with regard to the location of such systems. A technique which avoids the need for using laser light has been successfully used and was based on the use of a polychromatic light source to address particles captured on part of a particle filter which was chromatically analysed. Part of the filter was used as a reference area (Reichelt et al., 2006; Jones et al., 2008). The system was further developed to monitor airborne particle pollution using urban closed-circuit television camera (CCTV) networks for monitoring the particle capturing unit remotely (Kolupa et al., 2010). The chromatic technique has more recently been used as a line-of-sight approach based on combining a narrow-band chromatic source with a polychromatic source and an optical path several meters long in free air (Sufian and Spencer, 2018).
