associated with direct and indirect effects of aerosols in the climate. According to the authors, lightabsorption is one of the most difficult parameters to measure.Among the employed techniques that are based on aerosol absorption measurement,Giechaskiel et al. [24] mentioned (i) the difference method, in which the absorption is obtained from thedifference between extinction and scattering, (ii) the methods based in filters that measure lightattenuation by the PM collected in a filter, (iii) the methods based on photoacoustic spectroscopy and(iv) the methods based on Laser Induced Incandescence (LII). The last two methods measure BC throughparticle heating. The heating is caused due to light absorption by the particles.(i) Spotmeters—These equipments are also known as reflectometers or smoke filter meters, due tothe light absorption measuring principle based on light reflection over a filter. In a Spotmeter, theconcentration of particles is obtained by filtering the exhaust gas in a paper filter, and recording of theratio between the light reflected by this exposed spot and a non-exposed spot, as explained byGiechaskiel et al. [24].(ii) Aethalometer—As with Spotmeters, the Aethalometers are instruments used to determine BCconcentrations. According to Giechaskiel et al. [24] and Krecl et al. [35], PM is collected inAethalometers using a filter of quartz fiber. A change in light transmission (absorption) is measured inthe filter, in several wavelengths. For Krecl et al. [35], the Aethalometer is one of the optical instrumentsbased in filters, which is most used to determine the content of light absorbing carbon (LAC), besidesthe Particle Soot Absorption Photometer (PSAP). However, Giechaskiel et al. [24] pointed out that theconventional Aethalometers have a time resolution of several minutes, which is useful for environmentmonitoring, but slow for transitory emission tests. Versions with time resolution of 1 to 10 s becameavailable more recently.PSAP and Aethalometer measuring principle is the same, as stated by Krecl et al. [35]. According tothe authors, these equipments are based on properties of light absorption by carbonated aerosols. Theymeasure the attenuation of light transmitted through particles that are continuously collected in a filter.In the experiments by Krecl et al. [35], an Aethalometer series 8100 (Magee Scientific, Berkeley, CA,USA) was used to determine the concentration in mass of LAC in PM1. The aerosol deposited in thefilter were lit by a 880 nm LED and a 525 nm LED, for measures using the Aethalometer and thePSAP, respectively.Gong et al. [5] used a seven-wavelength aethalometer to measurement of the mass concentration ofBC and aerosol absorption coefficient.(iii) Photoacoustic Soot Sensor (PASS)—Light absorbing particles contained in the aerosol samplesare periodically heated by absorption of amplitude-modulated light. According to Giechaskiel et al. [24],the heat conducted from the particles to the surrounding gas generates acoustic pressure waves that areregistered by a microphone. The registered signal is proportional to the concentration in volume oflight-absorbing particles 300 nm).Lack et al. [34] developed a very sensitive method to measure aerosol absorption in 532 nm, with anexcellent response time, and they used photoacoustic absorption spectroscopy.(iv) Laser Induced Incandescence (LII)—According to Giechaskiel et al. [24], in LII, particles areheated right below the carbon sublimation temperature. Particle heating is done by a short laser pulse.After heating, particles reach incandescence and are decomposed. Particle decomposition is measuredby a photomultiplier. According to Santoro and Shaddix [36] the incandescence intensity and