Encyclopedia
20th class
20th class - zones in which flammable dust-air mixtures have a lower concentration limit of flame propagation less than 65 grams per cubic meter and are present continuously1;
2008. No. 30. Art. 3579.
Federal Law No. 123-FZ of July 22, 2008 "Technical Regulation on Fire Safety Requirements", as amended on July 1, 2019, Article 19, subpara. 4 // RSZ RF. ↩