Juan works with various metals. At the end of the day, he reclaims and separates each metal by using an inexpensive toxic acid though other methods are available. The risk of fire as well as health dangers to Juan is unknown. He should:

Review the safety sheet of the acid used in the separation of metals, in this way he can identify the toxicity and the possibility of fire caused by the same substance.
In case the substance is very dangerous, Juan must choose to use one of the other methods of separation available, in order not to put at risk his integrity.
In case the safety sheet does not classify it as very risky and instead saves you a lot of time, it is recommended that he uses protective implements and continue using the current method.

Explanation:

It is extremely risky to use a substance of which its effects are not known, therefore, whenever it is intended to use an unknown substance, the safety sheet provided by the distributor of the same must be verified, in which they are specified from the risks for its use, the recommendations when using it or storing it, as well as the implements that a person who manipulates said substance should use.