 Hornonitrianske Bane (HNB) Prievidza, a.s coal mine in Handlová is known as a rich source of Slovakia’s best-quality brown coal, however it also ranks among the most dangerous mines in the country because it is literally full of methane, a very explosive gas.The mine is equipped with sensors to monitor the concentration of methane in the air and whenever the concentration rises to an explosive level, the electrical installation in the whole mine is switched off and miners are signalled to leave.Coal extracted from mines in the Upper Nitra region is also 10 times younger than the hard black coal in the Ostrava region, which means that it is considerably less stable and poses a higher risk of rock-slides.