Scuba Assignment
Jordyn-Jayne Landon

Welcome to your introduction into SCUBA diving. Self-Contained Underwater Breathing Apparatuses or SCUBA has become a popular recreational and educational activity. There are various important aspects of SCUBA diving that you need to understand before you strap on your tank and dive into the depths. The key components of SCUBA diving that will be explained include equipment needed, safety and problems which can occur, what role the gas laws play in scuba diving, dangers and how to plan your own dives from the PADI table.

Gas Laws:
Gas laws play an extremely important part in scuba diving theory. Understanding gas laws is crucial to understanding the physics of scuba diving. Before diving you should be aware of the physics affecting you underwater, without this knowledge of what can happen to the human body under water, circumstances could easily become disastrous.

The change in pressure associate with diving has a major effect on divers and their equipment. Boyle’s Law states that the pressure of a gas is inversely proportional to volume at constant temperature, so as the pressure of a gas increases, the volume decreases. In turn, as the pressure decreases, the volume increases. In an inverse relationship, the product of two variable quantities is constant. So the product of pressure and volume at any two sets of pressure and volume conditions is always constant at a given temperature. As you go deeper, your body is subject to more pressure, for every 10 metres another atmosphere is added which causes the air you breathe to become more dense. The mathematical expression of Boyle’s law is P1V1 = P2V2.

The BCD is directly affected by Boyle’s law in that as the diver ascends, the pressure decreases and the air inside the BCD will expand. The law describes the inversely proportional relationship between the absolute pressure and volume of a gas, if the temperature is kept constant within a closed system. This is why it is important to release air from your BCD during both the descent and ascent to ensure it doesn’t rupture.

While diving it is vital that you do not hold your breath while ascending. The expanding air in your lungs will have nowhere to go, so your lungs will become over inflated causing overexpansion injuries, chest pain is often a sign of early injury. This occurs because it is the inverse relationship of pressure and volume of Boyle's Law that creates the pump - vacuum activity that allows for us to breathe, holding your breathe causes your lungs to fill beyond capacity with the re-expanded air. This can easily be preventable by simply breathing naturally and continually.

Pressure can also build up around the divers’ ears which can cause ear barotrauma; the results of this are usually ringing in the ear, dizziness and deafness in extreme cases. When descending the water pressure increases, since the outer ear is effect by the pressure of the surrounding environment the pressure increases, however the middle ear is sealed so the pressure inside doesn’t change. If equalising is not done the increased pressure in the outer ear relative to the middle ear flexes the eardrum inwards creating the discomfort. This can be avoided by simply pinching your nose closed and gently breathing out against your pinched nostril. Ear pressure equalisation is usually accompanied by a popping sound and a sensation of fullness in the ear. This can be avoided by equalising frequently when ascending and descending.

Charles’s law states that if a given quantity of gas is held at a constant pressure, its volume is directly proportional to the absolute temperature (Kelvin). Think of it this way. As the temperature of the gas increases, the gas molecules will begin to move around more quickly and hit the walls of their container, with more force the volume will increase. The mathematical expression of Charles’ law is V1/T1 = V2/T2.

Charles’ law applies when filling the scuba cylinders. When