Aim: To carry out an evaluation of pine needles moisture content, an important factor which contributes to fire hazards as a result of dielectric properties. Such an evaluation facilitates a speedy diagnosis of a fire hazard in pine forests An analysis was performed on the impact of physical and chemical properties of pine needles on the potential fire hazard.

Introduction: Moisture content of pine needles has an impact on properties associated with fire hazards. Traditional moisture determining methods consume much time and require specialist pre-calibrated measuring instruments and techniques. Therefore, the article proposes a method of evaluating pine needles moisture content, based on dielectric permittivity principles, expressed by the capacitance of a capacitor containing pine needles located between its plates

Project and methods: Experimental studies of dry pine needles were performed in a laboratory. Pine needles were stored at the constant air temperature of 20 ± 1°С and relative humidity of 46 ± 2% until uniform moisture content was achieved. Subsequently, the pine needles were dried for 2 hours, in an oven, at a temperature of 100 ± 5°C. The moisture content of pine needles was determined for each day of research by weighing , using laboratory scales. The dielectric permittivity of pine needles was evaluated with the aid of a flat capacitor, by placing a specified number of pine needles between its plates. This capacitor was connected to a capacitance measuring device . Statistical analysis methods and corresponding software were used for data processing.

Results: Dielectric permittivity changes were mapped using changes to the capacitor’s capacitance, with pine needles located between its plates. Identified the dependence relationships between moisture content of pine needles and drying time, as well as capacitance of the capacitor containing pine needles and drying time. Capacitance is proportional to dielectric permittivity, therefore, dielectric permittivity falls in parallel with a decrease in moisture content. Using regression analysis, linear and polynomial trends were identified , describing the dependence relationship between moisture content of needles and capacitance. Direct quantification of dielectric permittivity of pine needles is complicated by the presence of air among pine needles located between plates. Therefore diagnosis of a fire hazard should be performed using capacitance of a capacitor with pine needles between its plates rather than dielectric permittivity.

Conclusions: Evaluation of pine needles moisture content, with pines located between the plates of a capacitor, has an impact on the capacitor’s capacity, which facilitates a speedy prediction of fire hazard levels.

Keywords: fire hazard, pine needles, moisture, capacitor capacitance, scots pine, dielectric permittivity

Type of article: original scientific article