Learn Hardcore Spanish (Spain): Si la situación empeora, será más peligroso usarlo. - If the situation gets worse, it will be more dangerous to use it.

Unlikely: Si la situación empeorase, sería más peligroso usarlo.
Here you switch to imperfect subjunctive (empeorase) and conditional (sería) for a more hypothetical scenario.

Why do we say será más peligroso instead of estará más peligroso?

In Spanish, ser describes inherent qualities or characteristics, while estar describes temporary states or locations.
Danger is viewed as an inherent quality of the action or object, so we use ser:

Es peligroso usar esa máquina.
If you said está peligroso, it would sound odd—danger isn’t a temporary “state,” it’s a characteristic. Hence será más peligroso.

Why is there a comma after the si-clause, and can it be omitted?

Standard Spanish punctuation requires a comma when the subordinate clause comes first:

Si la situación empeora, será más peligroso usarlo.

If you reverse the order, the comma becomes optional:

Será más peligroso usarlo si la situación empeora.
In that case you can omit the comma (though some writers still include it for clarity).

Why is the direct object pronoun lo attached to the infinitive usar, forming usarlo? Could it go somewhere else?

In sentences with an infinitive, Spanish lets you attach the pronoun to the end of the infinitive:

…será más peligroso usarlo.

Alternatively, you could place lo before the conjugated verb if there were one in that clause, but since será is intransitive here, the pronoun must attach to usar. Compare:

No lo voy a usar.
Voy a usarlo.
Same logic: pronoun either precedes the finite verb or attaches to the infinitive.

How do I know what lo refers to?

Lo is a masculine singular direct-object pronoun. It stands in for a previously mentioned masculine noun—in context maybe el dispositivo, el aparato or el contrato, etc. If the thing you’re referring to were feminine, you’d use la instead. Without context, readers understand lo as “it” (something masculine/inanimate) mentioned earlier.

Why does más carry an accent? What’s the difference between mas and más?

Más (with accent) means “more” or “plus.”
Mas (without accent) is an old literary conjunction meaning “but” (similar to pero).

Since here we mean “more dangerous,” we need más with the accent.

Could I use en caso de que or cuando instead of si in this sentence?

Yes, but each has its own nuance and grammar:

En caso de que always triggers subjunctive:
“En caso de que la situación empeore, será más peligroso usarlo.”
Cuando for a future event usually takes subjunctive as well:
“Cuando la situación empeore, será más peligroso usarlo.”
Si with the present indicative (empeora) focuses on a likely condition.

Use si for straightforward “if” scenarios; use en caso de que to stress “in the event that,” and cuando when you assume it will happen eventually.

Why not use the conditional sería más peligroso instead of the future será más peligroso?

Using sería (“would be”) turns it into a more hypothetical, less certain outcome:

“Si la situación empeora, sería más peligroso usarlo.”
This suggests you’re speculating or being more tentative.
Using será (“will be”) states the result as a straightforward future fact, which is exactly what a Type 1 conditional does in Spanish.