English

The aim of the study was to evaluate the effect of humidification on the odour, acceptability and stuffiness of indoor air. The air of two wings of an office building in turn were ventilated with air of 30%-40% humidity in a six period cross over trial. The third wing was used as a non-humidified control. A panel assessed the quality of indoor air weekly. Mean intraindividual differences were used to assess the roles of sex, current smoking and age. The study found that humidified air was regarded as more odorous and stuffy than non-humidified air.

The ventilation system of a community hospital deteriorated progressively over a period of years until it no longer met regulatory guidelines. The publicly funded military facility hospital asked for funding for repairs but they were not available. The funding request was met when an increase in infections was identified and high-risk operations had to be curtailed. The problems were solved entirely when the new ventilation system was in place.

The study compared the atmospheric burden of viable particulates in the interiors of condominium homes with central air conditioning with that of the typically more open type of naturally ventilated Hawaiian residence. Enumeration of the numbers and types of respirable fungi and bacteria inside were done using Andersen microbial air samplers. To evaluate the impact of the air conditioning system on indoor air quality the results were compared with those obtained outside the homes.

The survival of bacterial and mould spores in new and used air filter media is explored. Samples of different media were challenged with specific microbial aerosols in a filtration test unit, and the viability of the microorganisms collected in the filter media examined. In five days there was no noticeable decrease or increase in the viability, nor did relative humidity have an influence.

In seven hospitals in the eastern United States air filters of various types, selected by discoloration, were collected from the primary and secondary filter banks of the HVAC systems. The samples were then examined with direct microscopy for fungal colonization. Results showed that filters from five of the hospitals were colonized with fungi. Several of the species had not previously been reported to colonize air filters.

Describes how new and used cellulosic air filters for HVAC systems including those treated with antimicrobials were suspended in vessels with a range of relative humidities, and containing non-sterile potting soil to stimulate fungal growth. Prior to suspension in the chambers most filters yielded fungi, but only two of 14 non-treated filters demonstrated fungal colonization following use in HVAC systems. Antimicrobial-treated filters, in particular a phosphated amine complex showed a lot less fungal colonization than nontreated filters.

Sensitizations to fungi that can be isolated when the fungi are removed from air conditioners are often shown by people suffering from various symptoms while in air conditioned rooms. It was shown that by using specific challenge tests fungal spores in air conditioners can give rise to allergic symptoms. The specific therapy prescribed for these reactions was hyposensitization. After this therapy, more that 70% of the patients could live and work again in air conditioned rooms without developing symptoms.

In the study a collection was made of bacterial and fungal spore samples from twelve office building ventilation systems. Measurements were performed with and without humidification. In none of the cases were ventilation or humidification systems found to act as bioaerosol sources. There was no observed difference between bioaerosol counts in offices with and without humidification. In all ventilation systems the microbial levels decreased.

An examination was conducted of thirty single family homes with either high or low house-dust mite allergen levels in mattress dust, with regard to ventilation, thermal climate, and air quality. High concentrations were associated with the difference in absolute humidity between indoor and outdoor air, also with low air change rates, especially in the bedroom. The research found no correlation between concentrations of TVOC or formaldehyde in bedroom air and HDM allergen concentration.

Describes and investigation of house-dust mites in 96 Danish homes with one or more members with asthma. All the homes were measured for air exchange rates, humidity and temperature. The study found a positive correlation between indoor air humidity and mite concentration and an inverse correlation between house-dust mite concentration and indoor air exchange. House-dust mite concentration was higher in the houses with mite-allergic persons. In 76% of the homes the concentration was above the proposed limit of 10 mites/0.1 g dust. This was so in 48% of the non-allergic homes.