# Influence of Grit Size and Wood Species on the Granularity of Dust Particles during Sanding
## 1 Introduction  
Wood dust is a waste generated during mechanical wood processing in wood industry plants. Dust poses a threat to workers health, increases the risk of explosion and fire, accelerates the wear of machines, worsens the quality of processing, and incurs high costs for its removal. Dust with particles smaller than 10 \(\upmu\)m affects the respiratory system, eyes, and skin, causing health effects in the form of irritation, allergies, and diseases [1; 2; 3; 4; 5; 6]. The dust toxicity is determined to a large extent by the type of wood raw material, which results from the different contents of the main chemical components, such as cellulose, hemicellulose, and lignin in coniferous and deciduous trees [7; 8]. Long-term inhalation of air polluted with wood dust, including the most harmful (i.e., beech and oak wood) may contribute to cancer incidence. As a result, wood dust was classified by the InternationalAgency for Research on Cancer (IARC) among the most dangerous and carcinogenic materials for humans. According to Directive 2004/37/EC of the European Parliament and of the Council of 29 April 2004 on the protection of workers against the risks related to exposure to carcinogens or mutagens at work; its current limit is 3 mg/m\({}^{3}\). After 17 January 2023, it will be reduced to only 2 mg/m\({}^{3}\). To meet such high requirements, it will be necessary to use all available technical means of dust reduction. The dustiness of the air inside production plants causes a fire and explosion hazard. Dust dispersed in the air can create an explosive mixture and settle on walls, floors, and machines, creating a risk of fire and explosion at the workplace. The inflammability of wood dust favors the spread of fire [9; 10; 11; 12; 13]. Extraction devices designed to remove dust from processing areas are never completely effective, especially in relation to the very small-sized dust particles. One way to reduce the amount of fine dust generated is to reduce the thickness of the furniture components and thus the diameters and depths of the holes for connectors, which reduces the volume of wood material cut. Such a procedure is effective in eliminating drilling and milling operations; however, it requires the development of new furniture fasteners [14] and does not reduce the need for sanding operations. Another way is to adjust the processing parameters to the type and properties of the material being processed. Appropriate adjustment of the treatment parameters will result in the formation of a reduced amount of fine dust dispersed in the air, could constitute a potentially dangerous inhaled fraction. With regards to sawing and milling, the technological parameters of the processing, as well as the type and sharpness of the tools used, are particularly important. Among technological parameters, the feed per tooth, the feed rate, and the thickness of the cut layer have important influences on the amount and size of the created dust particles [15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25]. The largest amount of dust is generated during the sanding of wood; therefore, this technological operation is considered to be the source of the most serious hazards related to wood dust. The amount and size of the dust particles created when sanding wood depends on the type of sanding machine used: wide-belt, narrow-belt, or disc sanders. It is difficult to remove the dust from some special types of sanding machines, such as manual belts, discs, and oscillating sanders [26; 27]. Recent studies on the size of the dust particles created during the sanding of wood concerned some of the most commonly used wood species in the industry. These tests were carried out using various types of sanding machines and sandpapers with grain sizes typical for the basic technical requirements of sanding operations. Many times, the sandpaper type studied was limited to paper tapes with the grain size of P80.