Microbial Control in Archives, Libraries and Museums by Ventilation Systems
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English Slovak |
| ISSN: | ISSN 0034-5806 |
| Online Access: | http://www.viks.sk/chk/res_2_98_85_107.doc |
| Abstract: | Summaries. Many archive, library and museum in hot and humid regions of the world constitute microenvi-ronments in the building that are conducive to the growth of micro-organisms, on their collections. Conservators have often dealt with the problem through an extensive disinfection and cleaning of the collections which use harsh and toxic chemicals. Consequently, it became necessary to search for a safe, effective and locally sustainable solution for the problem. It is commonly considered that high relative humidity environments are the main factor for activity of micro-organisms on collections. However, ventilation has been proved to moderate the biodeterioration even when the objects contained high enough moisture for microbial activity. In the present work the efficacy of ventilation to arrest microbial growth and reduce activity in both contaminated air and historic objects has been investigated. Laboratory experiments were carried out using a 500-liter environmental chamber to simulate contaminated rooms in buildings. Specific ventilation requirements to control fungal and bacterial activities in the air and paper samples have been established. These constitute a safe, reliable, and low cost control method for fungal and bacterial contamination of historic objects. In addition, ventilation is an appropriate alternative to air conditioning for those buildings located in humid regions. Most importantly, it avoids the use of chemical disinfecting treatments. Conclusions. The use of even a low ventilation rate in a range of 0.48-1.2 ACH has been found to be effective in decreasing environmental contamination in a test chamber as well as in paper samples at 55-85 % RH and room temperature of 20-24° C. The germination of fungal spores is preventable. However, slightly higher fungal and bacterial activities were observed at temperatures above 24° C. The above ventilation rate is not difficult to achieve in a room, however, it is needed to maintain the air movement even in a difficult area where ventilating air may not normally reach. A high contamination by fungal mycelia causes retention of moisture in paper. In addition, metabolic water produced by fungi increases the moisture content of paper and the water activity level which induces germination of spores. Consequently, a decrease in temperature was detected in contaminated papers and measured by an IR temperature transducer. The IR temperature transducer has been found to be a sensitive tool to detect the influence of local air movements on contaminated paper surfaces, although it was not possible to detect the change of the moisture content of the paper samples. The higher the ventilation rate, the closer the environmental and surface temperatures. Consequendy, biodeterioration risk is higher if a large temperature difference is detected between the two. Therefore, measurements of the temperature on cellulosic materials could be used as an indicator for the microbiological risk. It was found that cellulose materials are more susceptible to be biodeteriorated when they are exposed to non-ventilated environments, although the RH and temperature are acceptable. This negative effect should be considered in historic objects exhibited in showcases. Aspergillus fumigatus, Penicillium commune, Rhizopus oryzae, Cladosporium herbarum and Thrichoderma viride stopped their growth at specific environmental conditions (ventilation rate above 0.71 ACH, 60% RH and 20° C). They re-started their activities when the ventilation rate was reduced to 0.12 ACH. This emphasizes the need for relatively continued ventilation. The use of ventilation is a safe, reliable and low-cost alternative to air conditioning for maintaining a preventive environment against biodeterioration of collections in humid regions. In addition, it avoids risks of possible build up of an unhealthy environment for occupants in buildings. This approach against fungal and bacterial infestation rather than use of dangerous chemicals will protect both collections and professionals from exposure. |
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| ISSN: | ISSN 0034-5806 |
