# Influence of the Pyrotechnic Igniter Composition Aging on Explosion Parameters of Dispersed Dusts
## 1 Introduction  
Explosions of dispersed dusts are characterized by certain parameters. According to the EN 14034 Standard, those are: P\({}_{\text{max}}\)--the maximum explosion pressure of the dust sample, (dP/dt)\({}_{\text{max}}\)--the maximum rate of the dust sample pressure increase, LEL--the lower explosive limit and MOC--the minimum oxygen concentration [1; 2; 3]. Determination of those parameters is determined by the ASTM E1226a and EN 14034 (1-4) Standards. The Standards specify the procedure and technical equipment necessary for the correct performance of the determination of explosion parameters. Non-compliance with the procedure, incorrect technical equipment and sample properties may have unfavourable effects on the attained values. This concerns mainly the values of Pmax and (dP/dt)\({}_{\text{max}}\). The explosion parameters can be affected by the shape and size of vessel, type of the igniter used, location of the igniter in the chamber, and the type and parameters of the disperser. The effect of the disperser on the samples was investigated by [PERSON] [4]. The influence of the disperser on the dust dispersion process and explosion parameters was investigated by [PERSON] et al. [5] and [PERSON] [6]. Explosion parameters are also affected by the sample properties, such as particle size and ratio, humidity, impurities, etc. Their influence has been studied especially byBartknecht [7], but one can also find the latest scientific publications that examine the issue of interest. For example, the effect of moisture was investigated by [8; 9; 10; 11], while the effect of particle size was investigated by [10; 12; 13], etc. The ASTM E1226a [2] and EN 14034 [1] Standards specify the igniter parameters determining the explosion characteristics of dispersed dusts. ASTM E1226A specifies the amount and composition of the pyrotechnic charge used (1.2 g, 40% wt. zirconium metal powder, 30% wt. barium nitrate, 30% wt. barium peroxide). When using an igniter according to the EN 14034 Standard, the main parameter is the calorimetric value of the released energy \(2\times 5\) kJ. Additional parameters of the igniter are the fuse head activation speed (10 ms) and the location of the igniter in a confined chamber [1; 2]. To ignite a combustible dust-air mixture and achieve explosion, it requires an ignition source with adequate initiating energy. Initiating energy for dust clouds is generally stronger than that for gases. The type and strength of an ignition source have a significant impact on the initiation and progress of explosion [14; 15]. The impact of the amount of initiation energy released from the igniter was discussed by [PERSON] [7], [PERSON] [16] and [PERSON] [17]. The energy of a pyrotechnic igniter could strongly affect certain explosion parameters, such as the K\({}_{\text{St}}\) values and the lower explosion limits of dust explosions in the standard 1 m\({}^{3}\) vessel and the 20 L chamber. [14; 15]  
Some parameters that have an impact on the measured explosion characteristics are discussed by [PERSON] [18]. An igniter in the environment of hybrid mixtures has a specific effect on the course and results of the explosion process. The impact of different types of igniters on explosion characteristics was investigated by [PERSON] et al. [19], [PERSON] et al. [20] and [PERSON] et al. [21] The authors found that various types of igniters (a spark, pyrotechnic, exploding wire or resistive) have an impact on the (dP/dt)\({}_{\text{max}}\) value. The measurement results of hybrid mixtures seem to have been affected by particular measurement conditions; the attained values of explosion parameters of dispersed dust may be both higher or lower. Although several researchers have reported the effects of ignition sources on determining certain explosion parameters of dust, little attention has been paid to the igniting behaviour of a pyrotechnic igniter itself or to its effect on the explosion dynamics, especially on flame propagation immediately after the ignition.