Smaller-scale inflatables (such as pool toys) generally consist of one or more "air chambers", which are hollow enclosures bound by a soft and flexible airtight material (such as vinyl), which a gas can enter into or leave from through valves (usually one on each air chamber). The design dependence upon an enclosed pocket of gas leads to a need for a very durable surface material and/or ease of repair of tears and holes on the material, since a puncture or tear will result in the escape of the gas inside (a leak) and the deflation of the inflatable, which depends on the gas's pressure to hold its form. Detectable leaks can be caused by holes (from punctures or tears) on the material, the separating of seams, the separating of valve parts, or an improperly shut or improperly closing valve. Even if an inflatable possesses no macroscopic leaks, the gas inside will usually diffuse out of the inflatable, albeit at a much slower rate, until equilibrium is reached with the pressure outside the inflatable.