Welding helmet: shade, switching time, standards
The helmet is the one piece of equipment that protects an organ you cannot replace. Two standards define whether it does its job, and two numbers decide whether you can see what you are doing.
The standards
EN 175 covers the shell: impact resistance, coverage, materials. EN 379 covers the filter cartridge: the shade range, the switching time and the four optical class numbers. EN 169 gives the shade scale itself.
A helmet without these markings is not equipment, it is a hat. The markings are on the cartridge frame and on the shell, and they are small — worth checking before buying rather than after.
Choosing the shade
The shade number depends on the process and the current: roughly 9–10 for low-current MMA, 11–12 for MIG/MAG at 200 A, 12–13 for high current. The shade calculator gives the figure for your case.
Setting the shade too dark is a real and underrated mistake. You cannot see the edges of the pool, so you lean closer to see — which puts your head into the fume plume and worsens your control of the arc at the same time. Pick the lightest shade at which the arc is comfortable.
Switching time
Quoted in fractions of a millisecond: 1/25 000 s is ordinary, 1/30 000 s better. In practice anything at or below 1/20 000 s protects the eye, because the damaging exposure builds over a longer period than that. What longer switching times cost you is comfort — the flash before the filter reacts is what makes eyes tired by the afternoon.
Watch the low-temperature specification too: many cartridges slow down below about −5 °C, which matters on winter site work.
The optical class numbers
1/1/1/1 means the filter is essentially a clean window at every angle. Cheaper cartridges rate 1/2/1/2 or worse, and the third and fourth numbers are the ones that produce eye strain: the shade varies across the field or changes as you move your head. For occasional use it hardly matters; for a full day of TIG it matters a great deal.
The unglamorous parts
The headgear determines whether the helmet is usable. A four-point harness with adjustable pivot distance can be set so the filter sits close to the eyes, which widens the field of view. Weight matters over eight hours; so does whether the helmet stays put when you nod it down.
Keep spare cover lenses. A spatter-pitted outer lens costs a few coins and ruins the view completely, and welders will often work through a whole job looking through one rather than spend two minutes changing it. The rest of the protective kit is covered in personal protective equipment.
Frequently asked questions
What do the four numbers on the cartridge mean?
Optical class, diffusion of light, variation in luminous transmittance, and angle dependence — in that order, each from 1 (best) to 3. 1/1/1/1 is the top grade. The last digit is the one you notice over a long day: a poor angle rating means the shade changes as you tilt your head.
Is a passive helmet worse than auto-darkening?
Not optically — a good passive filter is excellent. It is worse ergonomically: nodding the helmet down loses the exact spot you were about to strike, and that costs accuracy on tacks and on TIG. For occasional heavy welding a passive helmet is perfectly serviceable.
Does the filter protect me when it fails to darken?
From ultraviolet and infrared, yes — a compliant filter blocks those in both states, so you will not get arc eye from a cartridge that failed to switch. What you will get is a very bright flash and a headache. Test the cartridge against a lighter flame or the test button before each session.
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