This paper addresses the subject of engines for non coal non-gassy mine applications and presents a proposal for worldwide harmonized emission standards.Diesel-powered equipment is extensively utilized in underground hard rock and coal mines. This is due, to a great extent, to the efficiency and safety characteristics of the Diesel engine.Regulations are in place addressing the emission quality of these engines. Furthermore, sufficient mine ventilation must be provided in order to ensure that pollutant levels in the working environment don't exceed permissible levels.Historically, Diesel engines featuring Indirect Injection (IDI) combustion systems have been preferred for underground mining operation due to their cleaner exhaust gas characteristics. The ever increasing stringency of the emission requirements applicable to on-highway trucks has resulted in Direct Injected (DI) Diesel engines with emission characteristics equal to, or in some areas, better than IDI engines. Since DI engines are manufactured in large volumes, as opposed to the niche-type market represented by the mining market, the question arises as to whether DI engines represent an alternative to IDI engines.This paper provides an overview of present and future emission legislation applicable to underground non-coal mines in different countries and its effect on the selection of IDI vs. DI engines.Furthermore, a proposal for worldwide harmonization of mining emission requirements is presented.