Reaction time (how quickly the lens darkens) is very critical to safeguard the eyes. Professional helmets will typically offer switch speeds of 1/25,000th of a second or better. These slow response times will result in eye strain and potential flash exposure, especially when tack welding or making short welds.
Most welding needs will be met with a good variable-shade auto-darkening helmet. Some welders, however, prefer specialty helmets for specific jobs – i.e., lighter helmets for TIG welding or feature helmets for special industry requirements.
Field of view requirements vary from user to user, but most professional welders prefer larger fields of view (3.8″ x 2.7″ or larger) for better visibility and reduced neck strain. Larger fields of view are particularly handy for out-of-position welding.
Regular care includes cleaning lens and sensor, battery check and replacement, damages check, storing in a dry, clean location, and replacement of cover lenses in case they are damaged or scratched. Avoid storing in extreme temperatures.
Indications that a replacement is necessary are: cracked or broken lenses, slow or uneven auto-darkening function, pitting or helmet shell damage that can be seen, headgear degradation, or if the helmet is over 5-7 years old and used on a daily basis. Are cheaper welding helmets safe to use? Cheap helmets can provide very little protection but must at least meet minimum safety requirements (ANSI Z87.1 and EN379). Professional welders must be persuaded to invest more in quality helmets for better protection, comfort, and longer durability in the long run.
Fixed shade helmets have a lens that is permanently darkened (usually shade 10), whereas variable shade helmets have an adjustable degree of darkness (usually shade 9-13). Variable shade helmets are simpler to work with when using a variety of welding processes but are usually higher priced.
Battery life varies with use and model but is typically 2,000 to 3,000 hours of actual use. Replacement batteries are possible for most helmets, and some provide solar-assisted power. Low-battery warning on most helmets prevents catastrophic failure.
Auto-darkening helmets use LCD and sensors to detect the welding arc. The lens automatically darkens in a fraction of a second (typically 1/25,000th) when the arc is struck. Auto-darkening helmets are highly reliable nowadays and also include backup safety in the event of a faulty auto-darkening function.
For MIG welding, shade 10-11 would typically be prescribed. For TIG welding, shade 11-12 would typically be required, and for stick welding, shade 10-12 would be required. Plasma cutting would typically require shade 11-12. The actual shade required may vary with amperage and working conditions.