Developing Evaluation Methods of Indoor Air Quality for Information Processing Devices in Information Working Environments

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Recently, contaminants (VOCs, particles, ozone, etc.) emitted from various printers have become a serious issue in indoor environments. In this study, the particle emission from them was mainly characterized to obtain the effective countenneasures against it. A commercialized ink-jet printer (IP), monochrome laser one (MLP) or color laser one (CLP) was installed in a test chamber composed of dual clean booths. The emission rate, size distribution and charge one of particles emitted from it were measured. Further, their stability was checked by introducing them into a diffusion dryer followed by the comparison of their size distributions upstream and downstream of it. As a result, the particle emission rate from IP was in the order of 10^6 particles per sheet at the printing mode, while that from MKP and CLP was in the order of 10^7 at both printing and paper feed modes. These particles were dominanily less than 100nm, indicating that they were not directly derived from toner and main ink mists. Further, the stability tests revealed that the particles emitted at the printing mode are composed of nonvolatile residues and water. That is, ink mists, which are designated as "satellite" and finer than main ones, are entrained from the IP to result in solid dye particles of about 30 nm in size. For MLP and CLP, water and stryrene vapor are emitted from paper sheets covered with toner by heating them at the fixation step, and then are nucleated into nano-particlcs (about 35 nm in size). The formed particles gradually shrink to be stable residues that might be mainly composed of styrene polymer. Therefore, these findings confirmed that not only the countermeasures against the nano-particle emission but its regulation should be undertaken.