Multi-Wavelength Densitometer for Experimental Research on the Optical Characteristics of Smoke Layers

Abstract

A novel multi-wavelength densitometer was built for the purpose of continuous and simultaneous measurements of light obscuration in smoke layers, concurrently in five bands (λ = 450 nm, 520 nm, 658 nm, 830 nm and 980 nm). This device was used for determining transmittance and visibility in smoke parameters of a smoke layer from the fire of 1.00 dm3 of n-Heptane in a 0.33 × 0.33 m tray located in a test chamber (9.60 × 9.80 × 4.00 m3). The performance of the device was compared with a commercial Lorenz densitometer at 880 nm. Significant differences in measured value of transmittance were observed between the different sensors – from 65% at 450 nm (blue light), 80% at 658 nm (red light) to 95% at 980 nm (IR). The visibility in smoke, estimated following the theory of Jin for light reflecting signs (K = 3), ranged from 7.5 m (blue light) to 12 m (red light) and for the light-emitting (K = 8) signs from 18 to 32 m, respectively. The performed experiment has confirmed the applicability and added value of multi-wavelength measurements of light-extinction in fire experiments. The device was sensitive to temperature variations and requires active cooling and careful warm-up prior to experiments, to reach the expected sensitivity.

Remote Sensing of the Light-Obscuring Smoke Properties in Real-Scale Fires Using a Photometric Measurement Method

“…These procedures follow a correlation of the logarithms of the measured light transmission at different wavelengths with the calculated extinction efficiency as a function of the particle diameter. We ˛gr-zyn´ski et al have examined several multi-wavelength densitometers following a similar approach in a literature study [21]. They summarized that most of the apparatus are connected to bench-scale experimental setups like cone calorimeters, while only few devices exist that are meant to be used in compartment scale fires.…”

Time Series Classification with Multiple Wavelength Scattering Signals for Nuisance Alarm Mitigation

“…Recently, there has been research conducted on reducing false alarms by utilizing the scattering characteristics of various wavelengths. K. Li et al [7] conducted research to reduce false alarms by measuring the scattering coefficient and extinction coefficient through multiple photodiodes, and W. Wegrzyriski et al, measured characteristics using densitometers of various wavelengths [8].…”