Why is Region3 not detecting players inside it? :(

Okay soooooo I decided to make a poison gas area cloud that would damage people inside it. Here is the script:

debounce = false
local RegionPart = game.Workspace.Gas.GasHitbox
local pos1 = RegionPart.Position - (RegionPart.Size / 2)
local pos2 = RegionPart.Position + (RegionPart.Size / 2)
local region = Region3.new(pos1,pos2)

while true do
	wait()
	local partsInRegion = workspace:FindPartsInRegion3(region, nil,100)
	for i, part in pairs(partsInRegion) do
		if part.Parent:findFirstChild("Humanoid") ~= nil and debounce == false then
			debounce = true
			print("Player found in region!".. part.Parent.Name)
			local char = part.Parent
			char.Humanoid.Health = char.Humanoid.Health -5
			wait (1)
			debounce = false
		end
	end
end

Keep in mind, I put this in server script service and this mostly worked with one player until two of them are in it. Also it kind of lags behind now so the player takes damage even after they leave the area of effect. Help would be much appreciated.

Thanks!

All your issues come from the fact you're yielding in the for loop. After iterating over the first instance where a humanoid is found, the humanoid will be damaged, yield for 1 second, then continue the for loop. I'm not so sure why you have a debounce either, considering it'll always be false when the debounce is checked. Maybe you didn't want every part of the character to invoke damage?

Anyways here's my implementation of what a poison gas script may look like:

while true do
	local partsInRegion = workspace:FindPartsInRegion3(region, nil, 100)
	local humanoids = {} --This will store all the humanoids inside the region

	for i, part in pairs(partsInRegion) do
		local humanoid = part.Parent:FindFirstChild("Humanoid")
		if humanoid then
			humanoids[humanoid] = true --Store the humanoid as an index of the table. Indexes are unique, so there should be no duplicate humanoids
		end
	end
	
	for humanoid in pairs(humanoids) do
		humanoid.Health = humanoid.Health - 5 --You may also want to call :TakeDamage(5) on the humanoid instead *if* you want to respect forcefields
	end
	
	--Yield for 1 second before continuing the next check
	wait(1)
end