ISO 18144:2003 specifies a method for the sampling and determination of respirable suspended particles (RSP) and for the estimation of the RSP fraction attributable to environmental tobacco smoke (ETS). This method is applicable to personal and area sampling. This method is compatible with the determinations of gravimetric RSP, ultraviolet particulate matter (UVPM) and fluorescent particulate matter (FPM), which are also used to estimate the contribution of ETS to RSP.