Testing of electrostatic precipitators efficiency on fire smoke absorption

Smoke is produced in all accidental fires. It is involved from all kinds of combustible materials like insulation, surface layers, installations or interior equipment installed in a vehicle. From several fire accidents in road tunnels, even from small fires in vehicles, a severe amount of smoke is produced. This is related to the significant use of hydrocarbons, which constitute a great part of combustibles. The smoke production increases in the sequence, alkanes, alkynes, aromatics and polynuclear aromatics. The smoke poses a threat to occupants and to fire brigade personnel regarding obscuration of tunnels and escape routes. Some tunnels have already installed Electrostatic Precipitators for cleaning up road dust. On behalf of the Norwegian Public Roads Administration, the precipitator effect on fire smoke is tested out. A series of bench scale tests were carried out where the increase of visibility is measured while smoke passes an Electrostatic Precipitator. The exhaust gases are sucked through a smoke channel for measurements. An electrostatic filter is placed in series with measurement probes of light obscuration, gas species (O-2, CO2 and CO), temperatures and volume flow. Heat release from the combustion is calculated by the oxygen consumption technique, and visibility is calculated from the light obscuration measurements and particle collection. The fire sources are Heptane fuel beds alone or in combination with plastic items. The experimental input parameters are thermal power of the fire, type of combustibles and gas flow velocity through the filter. Additionally a full scale experiment is carried out in a road tunnel where such electrostatic filters were installed. A small vehicle loaded with extra tyres were placed in a tunnel and the effect of the Electrostatic Precipitator was measured in terms of visibility. This project was sponsored by the Norwegian Directorate of Public Roads.