Electrostatic guarding of bookshelves for mould-free preservation of valuable library books
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Old books are highly susceptible to mould infection, and an effective method for avoiding moulding is needed to safely preserve valuable books in library stack rooms. Guarding a bookshelf with an electric field screen is a physical method that prevents airborne spores from entering the space used for book preservation. In this study, insulated conductor wires (ICWs) were used as electrodes to form electric fields. The ICWs were arrayed in parallel and linked to each other and to a direct current voltage generator. The electric field screen consisted of two layers of ICWs, which were negatively and positively charged with equal voltages to make dipoles, ICW(−) and ICW(+). Both ICWs generated an attractive force that captured airborne spores of Penicillium digitatum that were blown inside the screen. The attractive force was directly proportional to the applied voltage. At ≧0.9 kV, the screen exerted sufficient force to capture all airflow-carried spores, but a few spores that were once captured were repulsed out of the electric field when subsequent spores were attracted to positions proximal to them. This phenomenon was explained by creeping discharge between spores located close to each other on the ICW surface. This spore-repulsion problem was resolved by adding an additional ICW layer to the electric field screen, namely an electric field screen with an ICW(−) layer on both sides of an ICW(+) layer. The present study demonstrated that the three-layered electric field screen remained mould-free inside a screen-guarded bookshelf, irrespective of continuous spore exposure.
KeywordsElectric field screen Penicillium digitatum Creeping discharge
This work was supported by JSPS KAKENHI Grant Number 25450375.
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