First decide what the head needs protecting from. A safety helmet to EN 397 or IS 2925 is made for falling objects and impacts: Karam offers ISI marked helmets to IS 2925:1984, helmets to EN 397:2012+A1:2012 and models stated to both, plus one ABS helmet to ANSI/ISEA Z89.1-2014 Type 1, Class G and E, while Delta Plus states its ONYX, DIAMOND V, QUARTZ, SUPER QUARTZ and ZIRCON helmets to EN 397. A bump cap to EN 812, such as the Delta Plus AIR COLTAN or the Karam ABS bump cap, only guards against knocking the head on fixed objects and is not a substitute for a helmet where anything can fall.
For electrical work, look for EN 50365, the standard for electrically insulating helmets on low voltage installations. Delta Plus states EN 50365 Class 0 on ONYX, DIAMOND V, QUARTZ UP III, SUPER QUARTZ and QUARTZ I, with insulation up to 1000 V AC or 1500 V DC listed on several of them, and Karam states EN 50365:2002 on its ventilated peak, peakless and quadro corrugated models, with a 5 kV proof test and a 10 kV withstand test listed. For hot work, the EN 397 MM mark covers molten metal splash and LD lateral deformation, and the temperature marks show the tested range: -10°C to +50°C on QUARTZ I and ZIRCON 1, -30°C to +50°C on DIAMOND V and the QUARTZ UP models, and -30°C to +150°C on the ABS-PC SUPER QUARTZ for steel industry trades. The Karam Aironic adds an active cooling unit for hot, poorly ventilated areas of 40°C to 60°C.
Then choose for fit and comfort. Delta Plus helmets cover head sizes 53 to 63 cm, with the One-D Rotor knob on ONYX and QUARTZ UP (one hand, gloves on or off), push button sizing on DIAMOND V and SUPER QUARTZ, and manual sizing on QUARTZ I and ZIRCON 1. Karam offers slider, ratchet, pin-lock and wheel ratchet adjustment, breathable textile cradles, shuttered vents that close against rain, and Y type chin straps that keep the helmet in place. Peakless Karam helmets and the curved peak of the DIAMOND V widen the upward view for work at height. For face protection, the ONYX has a built-in retractable visor, ZIRCON 1 and several Karam helmets have slots for face shields and ear muffs, and FPS also supplies the VISONYXPR spare visor and HARNESS O spare harnesses for the ONYX.