You don't have much to worry about when it comes to getting Argon Poisoning. Argon itself is not classified as a poisonous gas, so getting poisoning from Argon is not possible. That being said, Argon can still be a very lethal and dangerous gas to work with, especially if you inhale way too much of it.
With the majority of welding helmet lenses being cheap, especially the plastic ones, why would someone want to take the time to clean them? They might be cheap but, after a while, all those dirty lenses and filters can add up to a lot of money you threw in the trash. Cleaning them will extend their life so you can use them even longer and save money. Plus, most lenses are extremely easy to clean and it should only take a few minutes of your time.
The short answer is Yes you can look at a solar eclipse with a welding helmet. According to NASA, you will be safe using a welding helmet with at least Shade 12, "Experts suggest that one widely available filter for safe solar viewing is welders glass of sufficiently high number. The only ones that are safe for direct viewing of the Sun with your eyes are those of Shade 12 or higher." Although most people (including myself) find that Shade 13 gives the most optimal view. Just don't go up to Shade 14 or else the solar eclipse will end up being too dark.
Welder's flash is a sensation of burning in your eyes that occurs after you have worked with a welding torch. Formally, the condition is called a corneal flash burn. It results in inflammation of the cornea. Some people also refer to the condition as arc flash burns. The cornea is the surface of the eyeball. In most cases, arc flash burns affect both of the eyes rather than just one.
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