On the issue of determining the main factors of gas hazard in coal mines of Ukraine Mykhailo Filatiev, Elvira Filatieva, Aleksandr Oleinichenko, Mihaela Toderas and Olga Kuderinova E3S Web Conf., 280 (2021) 08011 Published online: 30 June 2021 DOI: 10.1051/e3sconf/202128008011