Unless you are referring to a specific brand and product, that question has no definite answer.

However in general, if you dilute muriatic acid to about 12% (instead of 31%) the fuming stops. However, without special equipment, the fuming DURING dilution is so bad, it's easier to tell people how to handle it straight from the bottle.

Also, you really have to watch out for some of the "safer" products -- they are designed for surface cleaning, and have added detergents, etc. NOT what you want in your pool!