Soiling index used for -

(B) (Soiling index) (683 - Park 22nd)Smoke or Soiling Index:A known volume of air is filtered through a white filter paper under specified conditions and the stain is measured by photoelectric meter smoke concentration is estimated and expressed as micrograms/cubic meter of air as an average level over a period of time.* Best indicators of air pollution are sulphurdioxide, smoke and suspended particle**** Source of carbon monoxide indoor air pollution is combustion equipment, stove, Gas heaters.AIR POLLUTION INDEX* It is an arbitary index which takes into account one or more pollutants as a measure of the severity of pollution.* For example, the following index has been used in USA: 10 times the sulphur dio-oxide concentration plus twice the carbon mono oxide concentration (both in ppm by volume) plus twice the coefficient of haze.* It was considered to be a cause for alarm when the value of this index rose from its value of about 12 - 50 or more.