Sao Paulo State Environmental Protection Agency CETESB, Brazil, adopts a so called Reference Distance (RD) from hazardous substances storage facilities to populated places as a decision making tool for the application of a simplified or a full Risk Analysis (RA). As for hydrogen, RD was set up based on instantaneous release scenarios, where consequences reaching off-site population were estimated for delayed ignition ending up in vapor cloud explosion (VCE) with a 0.1 bar blast wave overpressure as a chosen endpoint, corresponding to a 1%2of death probability range. Procedures for RD evaluation and further adoption by CETESB are presented in this paper.