How to detect a player sitting?

Hello.

I have the following script, which is a modified version of the Fire Extingiusher. I'm making a fire turret, so i'm trying to make it so that it sprays from the nozzle. To do that, I need to make sure that the player is sitting.

Orginial Code:

local Tool = script.Parent
local spraying = false
local torso = nil
local offset = 5
local debris = game:GetService("Debris")

local bubble = Instance.new("Part")
bubble.Shape = 0
bubble.formFactor = 0
bubble.Size = Vector3.new(1,1,1)
bubble.Transparency = 0.2
bubble.BottomSurface = "Smooth"
bubble.TopSurface = "Smooth"
bubble.CanCollide = true

function onEquipped(mouse)

    torso = Tool.Parent:FindFirstChild("Torso", false)
    mouse.Button1Down:connect(onButton1Down)
    mouse.Button1Up:connect(onButton1Up)

end

function onUnequipped()

    spraying = false
    Tool.Handle.Mesh.MeshId = "http://www.roblox.com/asset/?id=27787143"
    Tool.Handle.FoamSound:Stop()


end

function onButton1Down(mouse)

    spraying = true
    Tool.Handle.Mesh.MeshId = "http://www.roblox.com/asset/?id=27787226"
    Tool.Handle.FoamSound:Play()
    sprayBubbles()

end

function onButton1Up(mouse)

    spraying = false
    Tool.Handle.Mesh.MeshId = "http://www.roblox.com/asset/?id=27787143"
    Tool.Handle.FoamSound:Stop()

end

function sprayBubbles()

    while spraying do

        local sprayDir = torso.CFrame.lookVector.unit

        local bubbleClone = bubble:clone()
        local torsoNormal = torso.CFrame.lookVector
        local denom = math.abs(torsoNormal.x) + math.abs(torsoNormal.z)
        local posX = 5 * (torsoNormal.x/denom)
        local posZ = 5 * (torsoNormal.z/denom)
        bubbleClone.Position = Vector3.new(Tool.Handle.Position.x + posX,Tool.Handle.Position.y,Tool.Handle.Position.z + posZ)
        bubbleClone.Velocity = Vector3.new(sprayDir.x,sprayDir.y + 0.5, sprayDir.z) * 50
        bubbleClone.Size = Vector3.new(math.random(1,2),math.random(1,2),math.random(1,2))
        bubbleClone.Parent = game.Workspace

        local script = Tool.ExtinguishScript:clone()
        script.Parent = bubbleClone
        script.Disabled = false

        debris:AddItem(bubbleClone, 2)

        wait(0.05)
    end

end

Tool.Equipped:connect(onEquipped)
Tool.Unequipped:connect(onUnequipped)

Thanks!