###### Abstract  
The issue of the formation of wood dust particles in the work environment is still an actual topic in terms of its impact on employee health and the risk of fire or explosion in a woodworking operation. This article deals with the characteristics of spruce dust (_Picea abies Karst_. (L.)), which was taken from several types of wood technology. Experimental samples of spruce dust were taken from four types of saving technologies, including grinding, friquetting and from the suction device container. The physical parameters of the samples taken were monitored and the particle size analysis was determined. The granulometric composition of the samples is significantly different. The sample of spruce wood dust from sawing has the most numerous fraction (250 \(\upmu\)m), while the sample from grinding has the most numerous fraction 63-250 \(\upmu\)m (87%).The aim of the paper was to monitor the minimum ignition temperature of the settled spruce dust layer and to look for a significant dependence of the minimum ignition temperature and ignition time on the type of spruce dust sample. A significant dependence was not confirmed. Significant moisture dependence of the samples was confirmed; the highest humidity was observed in the container, the lowest in sawing. s p  
Production residues are also subject to processes related to the reduction of the size of the wood, contributing to the formation of undesirable dust fractions [6]. The generation of dust during the handling and processing of materials can pose a risk to employees. This risk lies in the inhalation of the dust produced [7; 8; 9; 10; 11]. Wood dust poses a significant fire hazard, whether turbulent or settled [12; 13; 14].After ignition, the deposited dust may start to burn in the form of decay, incandescence and flame combustion [15; 16; 17]. When the available surface is greater, the process accelerates rapidly, increasing the emissions [18; 19]. Dust occurs in the environment in a wide range of particle sizes [20; 21; 22]. The particle size depends on the method of wood processing and its handling [23]. Particle size is one of the most important parameters of dust. Particle size measurement is commonly performed in various industries. Particle size is a critical parameter in production because it has a direct effect on the properties of the material or product, including reactivity [24; 25; 26; 27]. Wood dust is a set of several particles of different sizes and shapes [28; 29; 30], which is evaluated granulometrically [31; 32]. The fire-technical characteristics of an explosion is a set of parameters that includes [33]: upper and lower explosion limit, maximum explosion pressure, pressure rise rate, explosion constant, minimum ignition energy, ignition temperature of settled dust, ignition temperature of agitated dust, determination of susceptibility to spontaneous combustion and oxygen content limit. Distributions of combustible dusts in factories involved in dust explosions are described in detail in Zhi [34], with a dust explosion safety assessment. Monitoring the behavior of wood dust in terms of its ignition is carried out by determining the minimum ignition temperature of dust [35; 36; 37]. The ignition temperature of settled dust \(-t_{uMIN}\)- is the temperature that can be defined as the surface temperature at which spontaneous ignition of settled dust occurs [33].The \(t_{uMIN}\) temperature is used to determine the lowest hot surface temperature in equipment (\(t_{PRAC}\)) that can supply enough ignition energy to ignite the settled dust that comes into direct contact with this hot surface [38; 39]. [PERSON] [40] formulates the dependence of the danger of ignition of a settled dust layer according to [PERSON] [41] at the hot surface temperature \(t_{PRAC}\) (\({}^{\circ}\)C) by the Equation (1):  
\[t_{PRAC}\geq k_{b}\times t_{uMIN} \tag{1}\]  
where:  
\(t_{PRAC}\)--hot surface temperature in \({}^{\circ}\)C,  
\(t_{uMIN}\)--the minimum ignition temperature of settled dust,  
\(k_{b}\)--a safety factor of 2/3.