Educational Use Only — This tool demonstrates Gay-Lussac's Law for rigid scuba cylinders.

Gas Law: Temperature & Pressure

How temperature changes affect pressure in a rigid scuba cylinder (Gay-Lussac's Law)

Setup

Scenario

Cylinder

Temperature

189.1 bar 4 °C
12 L
Set up your scenario, calculate P2 in your head, then click below to check your answer.
Final Pressure P2
189.1 bar
Pressure Change ΔP
-10.9 bar
Usable Gas Change
-130.8 L
equivalent surface liters (ΔP × volume)
Dive Time Change at 20 m
-2.2 min
Surface Air Consumption 20 L/min at 3 bar (1+20/10)
Within working pressure (200 bar rated)

Temperature Range

💡 Why Does This Happen?

Gas molecules move faster at higher temperatures and hit the cylinder walls harder, increasing pressure. Since the cylinder is rigid (constant volume), all the extra kinetic energy translates directly to higher pressure.

Practical tip: Compressors generate significant heat during filling — gas inside a freshly filled cylinder can be 40–50°C above ambient. If you fill to 200 bar in a warm shop and dive in a cold lake, don't be surprised to see only ~180 bar on your gauge. That's not a leak — it's physics.

Rule of thumb: ~0.6 bar change per 1°C at 200 bar working pressure.

Gay-Lussac's Law (Isochoric Process)

P1 / T1 = P2 / T2
pressure / temperature ratio is constant at constant volume (T in Kelvin)
Rearranged:
P2 = P1 × T2 / T1