I thought buying a In-line rifle, but my area is very dry and I'm afraid of setting fire to the mountain for some detached spark the canyon.
Those who have these weapons have had some sparks problem?
Here it is impossible to find in pellet Powder, and the powder is found FFF Swiss grain, Powder is this dangerous?

I haven't used any Swiss powder but have used loose powder. There is some flashes outside the end of the barrel when firing but nothing I have seen that would set the woods on fire. Really not much different than pellets. bg

With an in-line you'll likely be using bullets with sabots or something similar. No worries at all with those projectiles and Swiss (or any other) powder.

There might be some concern if you were shooting patched round balls with a dry unlubed patch. The patch might still smolder when it hits the ground. But even a cloth patch is not a concern if it's well lubed.

these two posts +1 ^ ^ ^ ^ ^ ^

You will only start a fire if you fire your rifle with dry grass around the muzzle

I shot mine after dark to unload the gun and got VERY little flash using BH209 powder.
I had wondered the same thing since I hunt in tall grass and usually 10mph+ wind.
No concern about it now.