Having paid out a great deal of money to have his ventilation system cleaned the client is entitled to ask 'what do I do next. This short presentation will attempt to answer this question by way of a series of recommendations based on over 40 years experience in Building Services Engineering. The recommendations that I shall make will cover the following points:

Inner surfaces of the supply air delivery system are part of the indoor surfaces. This and technical performance make it important that cleaning of a HV AC system should be included in a proper maintenance program. Research work and cleaning actions have been done in many countries, however, the methods to verify the cleanliness varies and they seem to measure unequally the cleanliness. Filter sampling method is the most used method for determination of dust and debris amount on the surface.

A US company is using electric fields to remove airborne contaminants. Ewen Rose reports

Various studies on indoor and outdoor particulate matter in the urban environment in the vicinity of busy arterial roads in the centre of the subtropical city of Brisbane have indicated that the revised United States Environmental Protection Agency National Ambient Air Quality Standards (US EPA NAAQS) for P articulate matter PM2.5 could be exceeded not only outdoors but also indoors.

In connection with the research programme "Healthy Buildings", a building with indoor air quality problems was selected for further investigations. A Danish town hall was chosen because of many complaints over several years. A full-scale mock-up of a typical town hall office was built in the climate laboratory. A new heating and ventilating system and a new control strategy were chosen and implemented into the town hall.

Indoor air quality was monitored at two schools in Essex, UK (located on the same site) during the week 3--7 November 1997. The objective was to determine whether the ventilation rates within the buildings were adequate to provide acceptable air quality to the occupants. Airborne carbon  dioxide concentration was determined using continuous infrared detectors. A class base in each school was monitored for a two-day period. Occupancy patterns and window/door opening were observed during the first day of each period. Air temperature was also recorded.