ATEX directive. European Commission site (EU):
https://ec.europa.eu/growth/sectors/mechanical-engineering/equipment-potentially-explosive-atmospheres-atex_en

Amercian Petroleum Institute site (USA):
https://www.api.org/products-and-services/standards

IFA institute (EU) – big database about dusts
https://www.dguv.de/ifa/gestis/gestis-staub-ex/index-2.jsp

HSE Health and Safety Executive (UK) – lot of usefull (practical) information
https://www.hse.gov.uk/fireandexplosion/

National Institute of Standards and Technology (USA) – big data base about chemicals
https://webbook.nist.gov/chemistry/
https://webbook.nist.gov/chemistry/cas-ser/