What is safe PPE handling of diluted HCl and at what % should you use a face shield?

A. Hi John. Obviously disclaimers are needed here, and we need to start with #1 being what OSHA has to say on the subject. That is the law of the land and you can't do less; so if anything you read implies otherwise, it must be dismissed. You need to have a copy of the OSHA general industry standards on hand, become familiar with them, and refer to them whenever you are in doubt.

Disclaimer #2 is that it is impossible for someone miles away to determine, sight unseen, what is safe in your plant. There are always conditions and situations there that we readers would not be aware of.

But after those disclaimers, I think it is important to accept the law of unintended consequences and that you must evaluate your methods, standards, and safety program as an integrated whole rather than one item at a time. For example, if you terrorize someone that they must wear a faceshield when working with dilute HCl, and they form their own opinion from personal experience that it wasn't really very dangerous, what can you then tell them about working with concentrated HF that will get them to wear a faceshield (or even gloves!) when no one is looking?

So personally, I think you need to start "top down" and determine the greatest hazards in your location, concentrate on them, and as you work down to lower hazards, make sure that you don't (in an attempt to satisfy lawyers) cry wolf over lesser problems. So, if hydrochloric acid is the most dangerous thing you use in your plant, I'd require face shields when working with whatever strength you start at, even if 20%, because no shop should try to talk themselves out of ever needing face shields. But if you have HF or black oxide in the plant, I'd probably require goggles but not enforce face shields for HCl unless the danger looked quite real. But that's just me, and I'm retired :-)

Regards,