How do you put a player on fire when they touch something?

I know how to do an onTouched function:

function onTouched(part)

end

script.Parent.Touched:connect(onTouched)

But I'd like to know how to put the user who touched it on fire. I have a damage brick but I'd like a more realistic effect.

Damage = script.Parent.Damage.Value


function onTouched(part)
	local h = part.Parent:findFirstChild("Humanoid")
	if h~=nil then
		h.Health = h.Health - Damage
	end
end

script.Parent.Touched:connect(onTouched)

^ That is my script so far! I've tried many things like:

Damage = script.Parent.Damage.Value

function onTouched(part)
        local fire = Instance.new("Fire")
        fire.Parent = game.Players.LocalPlayer.Torso
        fire.heat = 5
        fire.size = 30
	local h = part.Parent:findFirstChild("Humanoid")
	if h~=nil then
		h.Health = h.Health - Damage
	end
end

script.Parent.Touched:connect(onTouched)

^ This script just breaks the entire brick! Thank you to everyone one who - tries to - help me!