Ventilation System Hygiene: A Review(TN 18/92 Technical Note)

This technical note aims to bridge various disciplines by reviewing published literature on the hygiene of ventilation systems. It provides designers with information to limit contamination, as well as aiding building owners in procedures to help mitigate the effects on the occupants of a building. Ventilation systems are often outside an employers' interest, and there is a perceived conflict of interest between occupational health and production. It is only when the workforce bring problems to their attention is any interest shown in the condition of the system. The hygiene of air conditioning and ventilation systems has frequently been neglected by building owners, largely as a result of long lengths of inaccessible ductwork being "out of sight and out of mind". Today, many buildings are refurbished, and where the air conditioning system is largely unaltered, duct cleaning is an important item often omitted in the refurbishment. Additionally, little is known about contaminants accumulating in ducts and their effect on indoor air quality, hence no firm guidelines have been established for procedures to inspect, maintain and clean these systems. The adverse publicity, absenteeism and reduced productivity associated with "the sick building syndrome" has put the spotlight on improving indoor air quality. It is almost certain that progressive litigation will ensure guidelines are established for keeping ventilation systems clean, to maintain a high level of air quality for the health and efficiency of occupants. Engineers do not generally have knowledge of such factors as microbiological contaminants and methods for their control. Also, knowledge gained from the study of microbiology has not been sufficiently available to engineers to apply in practical use. This report aims to remedy these shortcomings.

Table of Contents:
Legislation - United Kingdom, Scandinavia, France, USA; contaminants - sources of contaminants; micro-organisms - health effects; effects of dirt - health risks, reduced airflow, corrosion risk; limiting contamination - installation, contaminant sources, filtration, filtration indicators, air intakes, space allowance, working space around ductwork, drains, recirculation, cooling coils, humidifiers, floor grilles, environmental changes, standards; hygiene access doors; inspection - borescopes, rigid borescopes, flexible borescopes, video borescopes/micro-camera systems, ventilation system applications, remote-control inspection vehicles, filter inspection; cleaning and disinfection - ducts, filters, humidifiers - cooling coils, kitchen exhaust, cleaning frequency, ultra-violet lamp, UV lamps in air ducts; air sampling; further research.