Fog and blindness

A couple of years ago, I was running a game for family and friends. While in a very large antechamber, my son's character cast a "Fog" spell in front of the party. It effectively blinded the part and the monsters that I was controlling. It got quite confusing. I gave each player a hastily drawn map of the doom and had them track where they were at or had moved to on their turn. On the monsters turn, I showed the monsters movement and went by the honor system as to whether or not they bumped in to each other. It was challenging. I am still new and learning the ropes here. So, how can fog or blindness be handled in Roll20? In theory, if my monsters are caught in fog, and are blinded unless they have other sensory abilities, I should be able to see them but not the players characters unless they move out of the fog. It might be beyond the ability of Roll20 but I wanted to ask.

You could use Fog of War to cover the area of the fog. This would prevent players from being able to see through the area.

Fog of war should help you here. When player-controlled tokens are in a FoW area, they can see only their own token. Everything else: monsters, other PCs, maps, auras, all else is invisible-covered by black. To the GM however, the fogged area only appears lightly obscured. The transparency of this effect is variable from the page settings for that page. The GM can see everything. You can get more complicated than this with Dynamic lighting, but Fog of War should do you for what you describe.

Being blind does not makes everyone’s position unknown. There is still sound, if a creature does a hide check (which requires being unseen) then they can be unheard. In 5e if both parties are blind it effects spells and such that require sight ex “choose a target you can see”. For melee or ranged attacks you get advantage against a blind creature and disadvantage for being blind so you roll normal. To play like you did not only would everyone need to be blinded but also noise be taken away. 

Thanks Samuel W., but the issue here is not the rules of the game (which may or may not be 5th edition D&D). Rules discussions are off topic for the forums. The suggestions given were in order to achieve the effect that John B. is asking for.

As always, I appreciate everyone's input. Thanks