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At least 109 records · Page 6Linked to original sources
PubMed1990

Impact of heating and air conditioning system operation and leakage on ventilation and intercompartment transport: studies in unoccupied and occupied Tennessee Valley homes.

Forced-air heating and air conditioning (HAC) systems caused an average and maximum increase in air infiltration rates of 1.8- and 4.3-fold, respectively, during brief whole-house studies of tracer gas decay in 39 occupied houses. An average increase in air infiltration rate of 0.33 +/- 0.37 h-1 corresponded to an incremental air leak of 240 m3/h, based on approximate house volume. More detailed tracer gas decay studies were performed in basement, kitchen and bedroom locations of six homes with low air infiltration rates (i.e., less than 0.25 h-1). The HAC mixed the indoor air efficiently between measurement sites. HAC operation also caused 1.1- to 3.6-fold increases in air infiltration rates, corresponding to absolute increases of 0.02 to 0.1 h-1. In an unoccupied research house, three-fold increases in average air infiltration rate with HAC operation (i.e., from 0.13 to 0.36 h-1) were reduced to two-fold (i.e., from 0.10 to 0.18 h-1) by sealing the external HAC unit and crawlspace ductwork system. This sealing also resulted in a 30 percent reduction in crawlspace-to-indoor transport rates with the HAC turned on. Blower door tests indicated a less than 20 percent reduction in house leakage area.

Air Conditioning↗
PubMed1984

Ventilation and air conditioning--a primer for nonengineers.

Some aspects of ventilation and air conditioning have been explained for infection control personnel who are not engineers. With more understanding of ventilation, infection control personnel may be able to communicate better with engineering personnel on this subject.

Air Conditioning↗
PubMed2004

Effects of breathing pattern and inspired air conditions on breath condensate volume, pH, nitrite, and protein concentrations.

BACKGROUND: The effects of breathing pattern and inspired air conditions on the volume and content of exhaled breath condensate (EBC) were investigated. METHODS: Total exhaled water (TEW), EBC volume, pH, nitrite and protein concentrations were measured in three groups of 10 healthy subjects breathing into a condenser at different target minute ventilations (Vm), tidal volumes (Vt), and inspired air conditions. RESULTS: The volumes of both TEW and EBC increased significantly with Vm. For Vm 7.5, 15 and 22.5 l/min, mean (SD) EBC was 627 (258) microl, 1019 (313) microl, and 1358 (364) microl, respectively (p<0.001) and TEW was 1879 (378) microl, 2986 (496) microl, and 4679 (700) microl, respectively (p<0.001). TEW was significantly higher than EBC, reflecting a condenser efficiency of 40% at a target Vm of 7.5 l/min which reduced to 29% at Vm 22.5 l/min. Lower Vt gave less TEW than higher Vt (26.6 v 30.7 microl/l, mean difference 4.1 (95% CI 2.6 to 5.6), p<0.001) and a smaller EBC volume (4.3 v 7.6 microl/l, mean difference 3.4 (95% CI 2.3 to 4.5), p<0.001). Cooler and drier inspired air yielded less water vapour and less breath condensate than standard conditions (p<0.05). Changes in the breathing pattern had no effect on EBC protein and nitrite concentrations and pH. CONCLUSION: These results show that condensate volume can be increased by using high Vt and increased Vm without compromising the dilution of the sample.

Breath Tests↗
PubMed1991

Colonization by Cladosporium spp. of painted metal surfaces associated with heating and air conditioning systems.

Cladosporium cladosporioides and C. hebarum colonized painted metal surfaces of covering panels and register vents of heating, air conditioning and ventilation systems. Hyphae penetrated the paint film and developed characteristic conidiophores and conidia. The colonies were tightly appressed to the metal surface and conidia were not readily detectable via standard air sampling procedures.

Air Conditioning↗
PubMed1976

Subjective odour levels in an air - conditioned hospital ward.

Tests were carried out in an experimental air-conditioned hospital ward to determine what effect the mechanical ventilation and recirculation rates had on subjective odour levels in the ward. Odour conditions in the ward were not found to deteriorate with decreasing mechanical ventilation rate or increasing recirculation rate, but to fall into two distinct categories, which have been termed 'Acute' and 'Intermittent Background' conditions. 'Acute' conditions, where a particularly foul malodour prevailed in one or more rooms of the ward, were a rarity in the experimental general surgical ward; they occurred only twice during the testing period of approximately two years, and the mechanical ventilation rates tested were incapable of dealing with them. 'Intermittent Background' conditions, which are not attributable to a general prevailing odour level but rather to specific low level odour producing events, were satisfactory even under the most extreme test condition of three mechanical air changes per hour and 80% recirculation.

Journal Article↗
PubMed2004

Aeroallergen sensitization in pediatric allergic rhinitis in Singapore: is air-conditioning a factor in the tropics?

Singapore is a unique blend of a tropical environment with a high standard of hygiene and public health care. The objective was to define the prevalence, clinical characteristics, and environmental risk factors of specific aeroallergen sensitization in pediatric allergic rhinitis patients in this unique environment. The method adopted was a retrospective analysis of allergic rhinitis patients, undergoing aeroallergen skin prick testing (SPT), in the outpatient specialty clinic of the KK Children's hospital, from July 2001 to June 2002. A total of 202 patients were included, 161 (80%) males, 167 (83%) Chinese, age mean 7.6 yr (range 2-14 yr). The most prevalent clinical symptoms were: watery rhinorrhea 61%, blocked nose 61%, sneezing 52%, snoring 17%, and epistaxis 12%. SPT results were positive for house dust mites in 97% of children, pets (20%), molds (19%), pollens (15%), and kapok (10%). Mold sensitization was significantly more prevalent in households without air-conditioning (aircon), 49% vs. 10% with aircon (odds ratio 9.4, 95% CI 3.8-22.9). Polysensitization (sensitization to three or more allergens) was similarly more prevalent in households without aircon, 51% vs. 14% with aircon (odds ratio 6.4, 95% CI 2.8-14.7). It was concluded that indoor aeroallergen sensitization is the major associated factor with clinical allergic rhinitis in children in Singapore. Patients living in households without air-conditioning are at increased risk of mold sensitization and polysensitization.

Adolescent↗
PubMed2005

Fungal contamination of air conditioning units in operating theatres in India.

Postoperative fungal infections may be caused by discharge of spores from contaminated air conditioning (AC) units. The filters of such units may act as a nidus for the growth of fungi. In this survey, filters of AC units in 25 operating theatres in India were evaluated quarterly over two years. The overall rate of fungal colonization of the AC filters was 26%. In addition, window-mounted AC units had higher fungal counts than wall-mounted AC units. We conclude that although the exact load of fungal spores necessary to initiate infections is unknown, AC units in operating theatres should be meticulously maintained and frequently monitored to minimize the chances of growth and proliferation of potentially pathogenic fungi. Data from this study also suggest that the design of the AC unit may play an important role in reducing fungal spore counts in the air of operating theatres in developing countries.

Air Conditioning↗
PubMed1975

Airborne infection in a fully air-conditioned hospital. IV. Airborne dispersal of Staphylococcus aureus and its nasal acquisition by patients.

Studies in a newly built hospital furnished with complete air conditioning where most of the patients are nursed in 6-bed rooms showed that the transfer of air from one patient room to another was very small, especially when there was substantial flow of air in a consistent direction between the patient rooms and the corridor, and that the direct transfer of airborne particles was even less. There was, however, no evidence of any reduction in the rates of nasal acquisition of Staphylococcus aureus compared with those to be found in naturally ventilated hospitals. The numbers of Staph. aureus found in the air of a given room that appeared to have originated from patient carriers in other rooms were many times greater than could be accounted for by direct airborne transfer. Although there was evidence that many carriers were not detected, detailed study showed that this excess transfer to the air of other rooms was genuine. It seems probable on the basis of investigations in this hospital and elsewhere that this excess transfer occurs indirectly, through dispersal from the clothing of the nursing and medical staff into the air of another room of strains with which their outer clothes have become contaminated while dealing with patients. Reduction in direct airborne transfer of micro-organisms from one room to another, whether by ventilation or other means, can only be of clinical advantage if transfer by other routes is, or can be made, less than that by the direct airborne route.

Adult↗
PubMed1975

Airborne infection in a fully air-conditioned hospital. II. Transfer of airborne particles between rooms resulting from the movement of air from one room to another.

Experiments were conducted simultaneously with gas and particle tracers to determine the relative loss of particles between source and recipient sites in the hospital ward units. The magnitude of this loss could be accounted for by the assumption of sedimentation from well-mixed air masses during the time required for movement between source and recipients sites. As a consequence of this loss the degree of isolation between patient rooms for airborne particles was between 4 and 25 times greater than that for gaseous contamination, which reflects the actual transport of air between the rooms. The design and construction of portable spinning-disk particle generators suitable for field studies is discussed.

Air Conditioning↗
PubMed1978

Efficiency of bacterial filtration in various commercial air filters for hospital air conditioning.

Filtration efficiency of high-efficiency particulate air (HEPA) filters is said to be over 99.97% of removal rate against the mist of thermogenerating-type of dioctyl phthalate with average particles diameter of 0.3 micrometer, as tested by the U.S. Military Standard 282 (1956). Filtration of bacterial aerosols through commercial air filters was tested to examine the efficiency of bacterial filtration with eight kinds of air filters. Percentage of bacterial filtration efficiency (% BFE) of three kinds of HEPA filters showed 100% BFE, while NBS-95 and NBS-85 showed over 99% BFE. BFE of NBS-75 air filter was 91.75%.

Aerosols↗