Abstract. We characterized size and chemical composition of ions generated by a corona-needle charger of a Neutral cluster and Air Ion Spectrometer (NAIS) by using a high resolution differential mobility analyzer and a time-of-flight mass spectrometer. Our study is crucial to verify the role of corona-generated ions in the particle size spectra measured with the NAIS, in which a corona charger is used to charge aerosol particles down to the size range overlapping with the size of generated ions. The size and concentration of ions produced by the corona discharging process depend both on corona voltage and on properties and composition of carrier gas. Negative ions were <1.6 nm (0.8 cm 2 V −1 s −1 in mobility) in all tested gas mixtures (nitrogen, air with variable mixing ratios of water vapour), whereas positive ions were <1.7 nm (0.7 cm 2 V −1 s −1 ). Electrical filtering of the corona generated ions and not removing all charged particles plays an important role in determining the lowest detection limit. Based on our experiments, the lowest detection limit for the NAIS in the particle mode is between 2 and 3 nm.

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<p class="R-AbstractKeywords"><span lang="EN-US">Literature sources and earlier researches state that plants may be able to produce a variety of air ions, including negative light ions. In this article, the regularity of influence of plants on the number of ions in the room is being proved, basing on a series of experiments performed with the following plants: Spathiphyllum, Scindapsus, Strobilanthes, Chlorophytum and Pinus mugo. It was concluded that plants, in general, are able to stabilize the indoor ion concentration and reduce its fluctuations. The plants help to increase the concentrations of negative ions and decrease the concentration of positive ones, however the optimal and “healthy” ion concentration was not reached. Plants without artificial illumination work more as ion reducers, not producers.</span></p>

We characterized size and chemical composition of ions generated by a corona-needle charger of a Neutral cluster and Air Ion Spectrometer (NAIS) by using a high resolution differential mobility analyzer and a time-of-flight mass spectrometer. Our study is crucial to verify the role of corona-generated ions in the particle size spectra measured with the NAIS, in which a corona charger is used to charge aerosol particles down to the size range overlapping with the size of generated ions. The size and concentration of ions produced by the corona discharging process depend both on corona voltage and on properties and composition of carrier gas. Negative ions were <1.6 nm (0.8 cm² V^&minus;1 s^&minus;1 in mobility) in all tested gas mixtures (nitrogen, air with variable mixing ratios of water vapour), whereas positive ions were <1.7 nm (0.7 cm² V^&minus;1 s^&minus;1. Electrical filtering of the corona-generated ions and not removing all charged particles plays an important role in determining the lowest detection limit. Based on our experiments, the lowest detection limit for the NAIS in the particle mode is between 2 and 3 nm

Saturation of air ions is essentially important for all living beings, especially for human health. Existing sanitary norms provide that concentration of small ions has to be in range of 400-50000 ions cm-3 and unipolarity coefficient 0.4 ≤ K ≤ 1.0. Many species of indoor plants emit organic volatile compounds and air ions, therefore they could be used for improving the quality of indoor air. The results show that ionization level of indoor air is significantly insufficient and selected species of indoor plants are not able to improve it. They serve rather as supplementary surfaces for ion absorption. Possible interaction between microclimate, ion concentration and indoor plants in different times of the day is analyzed.