How Do Auto-Darkening Helmets Work?

Auto-darkening welding helmets are a blessing for welders. They get so much more work done when they don’t have to worry about flipping the lens up and down, adjusting the helmet to the amount of light produced by the arcs.

So how do auto-darkening helmets work?

Auto-darkening helmets have auto-darkening filter lenses. When activated, the helmet uses a shade #3 filter.

The protection this shade provides is like using a quality pair of sunglasses in bright daylight. Several light sensors placed near the lens help identify the filter shade needed.

As soon as you strike an arc, the sensors activate and switch the lens filter accordingly.

What are the components of an auto-darkening welding helmet?

An auto-darkening welding helmet is comprised of the following components:

The UV/IR filter

The UV/IR layer protects the welder from Infra-Red (IR) and Ultra Violet rays (UVR) whether the lens is activated or not. It consists of a thin glass layer with several metallic layers within.

The metallic layers consist of 5 layers of silver and 6 of aluminum oxide.

The metallic layers filter out IR radiation and also protect the liquid crystal panel from heat damage as well. For UVR, the filter works in combination with both the metallic and polarization filters to protect the welder from UV radiation.

The glass layer also filters out UV radiation. However, UVA radiation, which has more penetrative power, can make it through the glass.

For UVA, the metallic layers and polarization filters must be present to provide optimal coverage.

Polarization filter

There are three polarization filters in an auto-darkening helmet. There is a filter after every layer starting from the UV/IR interference layer.

All three combined help to protect the welder from the bright visible light of the arc.

The filter right after UV/IR is arranged at a 90-degree angle. When arranged at 90 degrees, these filters are at their darkest – they darken only slightly when arranged in the same line as the other layers.

Liquid crystals cell

Between the three polarizing filters lie two Liquid Crystal Cells (LCC). When stimulated by electricity, they have the power to bend light.

You can even manipulate how the filters turn the light and can also have the filter not refract the light at all.

Arc sensors + light sensors

Light sensors and arc sensors combine to determine the light intensity and darken the lens accordingly. There are multiple lights and arc sensors in a helmet.

Light sensors filter out the extra light in standard welding procedures, whereas arc sensors deal with intense bright lights as produced by welding arcs.

Before you start welding, you need to power up the helmet. Auto-darkening helmets start with shade three, and during welding, they can even reach shade 8 to shade 13, depending upon the luminosity of the arc.

Features to look for in an auto-darkening welding helmet

Before you purchase a helmet, there several factors to consider that will help you decide which helmet is right for you.

Viewing area

To maximize productivity, the viewing area of your lens must be sufficient. It should provide you with enough coverage to be able to view the project you are working on without much effort.

For added ease and comfort, you should opt for helmets with full coverage viewing lenses.

Functionality controls

These can be placed either inside or outside the helmets. They allow the welder to adjust the light sensitivity and other functionalities of the helmet.

The more comfortable they are to access by the welder, the better. Of course, the choice here will be subjective as not all welders are satisfied with the same design.

Most manufacturers design their helmets with internal functionality controls as that keeps them protected even through intense heat.

Light sensitivity

Light sensitivity is particularly important. That is what the helmet is primarily for. If the light sensors don’t appropriately identify and adjust the shades according to the light, then the helmet is useless. A faulty light sensor will cause the welder’s eyes to sustain a lot of damage as a result of the brightness of the arc.

Sensitivity controls

The main benefit of an auto-darkening welding lens is that welders don’t have to adjust the lens manually while they’re doing their work. However, not all eyes adjust to light intensity in the same way.

Some eyes are not comfortable with even relatively less intense light exposure, while others may be able to handle pretty harsh lighting conditions. Being able to adjust the setting according to your comfort level is an option many welders seek, which is why sensitivity controls are essential.

Delay control

Delay controls let you determine how long the lens will remain dark after the arc stops. With most delay controls, the welder can adjust the delay setting from 0 to 2 seconds. For shorter processes, the welder can set the delay timer for 0.5 seconds. For longer processes, they can set the delay timer for up to 2 seconds. This ensures that the welder’s eyes have time to adjust to the bright light (or lack of it).

Lens reaction time

The lens reaction time indicates how quickly the auto-darkening lens switches shades from light to dark. The quicker the lens adjusts itself, the better protection it offers.

If you’re dealing with weld arcs all day, then a slow reaction time from your lens can cause eye fatigue and can even cause severe damage. We suggest you opt for helmets with reaction speeds as high as 1/20,000 of a second.

Arc sensors

Some auto-darkening helmets have one or two arc sensors. With those helmets, there are higher chances that the shade lens will fail to get darker as the arc gets brighter.

For maximum eye protection, you should choose a helmet with at least four arc sensors.

Power source

Different helmets use different power sources – lithium-powered, rechargeable, changeable, and even solar-powered batteries.

Helmets with replaceable batteries tend to last longer, whereas helmets with non-replaceable batteries have a limited lifespan of 5 to 8 years. Solar-powered helmets last even longer, but you need to place them under the sun for at least a day before the welding job.

Comfort and helmet weight

Lastly, but most importantly, take into account the weight of the helmet and how comfortably it fits. Heavy helmets can give you a significant headache and make the experience a nightmare for you. Ill fitted helmets that keep falling off are also not ideal as they will not provide enough coverage.

Welding requires attention to detail and intense concentration. Choosing a helmet that provides excellent protection with comfort is as essential to producing a good weld, as is the welder’s skill set.

What are the best auto-darkening welding helmets available?

Here are a few of my favorite auto-darkening welding helmets:

3M Speed glass Welding Helmet 9100

3M Speedglas Welding Helmet 9100 06-0100-30SW, with ADF 9100XX, 1 EA/Case


  • Variable shade lenses: 5, 8-13
  • Viewing Area: 2.8 x 4.2 inches
  • Battery life: 2000 hours

The 3M Speed Glass Welding Helmet includes head protection and side windows for better protection and increased visibility.

Lincoln Electric Welding Helmet 3350

Welding Helmet, Black, 3350 Series


  • Lens Shade: 5 – 13
  • Viewing Area: 3.74 x 3.34 inches
  • Lens reaction time 1/25,000 sec

The Lincoln Electric Welding Helmet is one of the best helmets available on the market. Their 3350 model is a solar-powered helmet and provides unmatchable protection

Miller Electric Digital Elite Welding Helmet

Miller 281000 Digital Elite Black Welding Helmet with ClearLight Lens


  • Lens Shade: 3,5 to 8,13
  • Viewing Area: 9×9 inches
  • Lens Reaction Time: 1/20,000 sec

With its long-lasting battery life and high lens reaction speeds, the Miller Electric Welding Helmet lives up to its name and provides elite protection.

All helmets mentioned above meet the ANSZI Z87.1 – 2003 (also known as ANSI Z87+) standards. The ANSI standard is an indication that the helmet has passed independent testing for safety measures.

It judges them on their ability to protect against high velocity flying objects as well as UV radiation.

All helmets that have passed this standard provide 100% UV and infrared filtering regardless of the shade setting. The standard also tests whether the helmet delivers the advertised lens reaction time for both low and high temperatures.

Some helmets take time to switch shades in low temperatures, which can be detrimental to the eye health of the welder.

Related questions

Are auto-darkening welding helmets safe?

Yes, if used correctly, auto-darkening welding helmets are safe and do not damage your eyes.

Make sure you adjust the settings according to your comfort level. Try them out on smaller jobs before you use them for longer projects.

Do auto-darkening helmets go bad?

It honestly depends on your particular helmet. Some helmets with solar plates need more charging time after a few years of use.

If your helmet is rusting or is bent, then you should probably get it checked if it hurts your eyes when you use it.

How do you test an auto-darkening welding helmet?

To know that the helmet is ideal for you, first check its features. You need to know the different shade numbers it provides, the reaction speed, the weight, and whether it’s certified or not.

After picking out the one you think meets your needs, perform the sun test. Put on your helmet as you would if you were going to weld something.

Then, look up at the sun and note how fast and how dark your welding lens gets.

Some auto-darkening welding helmets will suit you, and some will make your eyes hurt. You won’t know which is best for you unless you test it out.

I suggest that you don’t skip out on the sun test when buying a helmet.

About Pierre Young

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Hey, I'm Pierre Young a qualified AWS Certified Welder. I got into welding in 2009 as a side hustle. Ever since then, I've been doing all kinds of welds - both for business and pleasure. While immersing myself in this wonderful hobby, I've learned from hands-on experience what welding gear works and what doesn't. Welding Headquarters is the site where I share everything I've learned.

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