E.S.I. Environmental Sensors Inc. (ESVFF: Grey Market) | Deleted Symbol Fri, May 15, 2020 12:00 - E.S.I. Environmental Sensors Inc. (ESVFF: Grey Market) - Deleted Symbol - As of Fri, May 15, 2020, ESVFF is no longer a valid symbol. You may find a complete list of deleted symbols at otcmarkets.com .