Household humidification is widely practiced to combat dry indoor air. While the benefits of household humidification are widely perceived, its implications to the indoor air have not been critically appraised. In particular, ultrasonic humidifiers are known to generate fine particulate matter (PM). In this study, we first conducted laboratory experiments to investigate the size, quantity, and chemical composition of PM generated by an ultrasonic humidifier. The mass of PM generated showed a correlation with the total alkalinity of charge water, suggesting that CaCO₃ is likely making a major contribution to PM. Ion chromatography analysis revealed a large amount of SO₄²⁻ in PM, representing a previously unrecognized indoor source. Preliminary results of organic compounds being present in humidifier PM are also presented. A whole‐house experiment was further conducted at an actual residential house, with five low‐cost sensors (AirBeam) monitoring PM in real time. Operation of a single ultrasonic humidifier resulted in PM_2.5 concentrations up to hundreds of μg m⁻³, and its influence extended across the entire household. The transport and loss of PM_2.5 depended on the rate of air circulation and ventilation. This study emphasizes the need to further investigate the impact of humidifier operation, both on human health and on the indoor atmospheric chemistry, for example, partitioning of acidic and basic compounds.

中文翻译：

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超声波加湿器排放的颗粒物——化学成分及其对室内空气的影响

家庭加湿被广泛用于对抗干燥的室内空气。虽然家庭加湿的好处已广为人知，但其对室内空气的影响尚未得到严格评估。特别是，已知超声波加湿器会产生细颗粒物 (PM)。在这项研究中，我们首先进行了实验室实验，以研究超声波加湿器产生的 PM 的大小、数量和化学成分。产生的 PM 的质量显示出与进水总碱度的相关性，表明 CaCO ₃可能对 PM 做出主要贡献。离子色谱分析显示大量 SO ₄ ^2-在 PM 中，代表以前无法识别的室内源。还介绍了加湿器 PM 中存在的有机化合物的初步结果。在实际住宅中进一步进行了全屋实验，使用五个低成本传感器 (AirBeam) 实时监测 PM。单个超声波加湿器的运行导致 PM _2.5浓度高达数百 μg m ^-3，其影响扩展到整个家庭。PM _2.5的传输和损失取决于空气循环和通风的速度。本研究强调需要进一步研究加湿器操作对人体健康和室内大气化学的影响，例如，酸性和碱性化合物的分配。