How Do Gas Laws Relate With SCUBA Diving?

Gas laws play an extremely important part in scuba diving theory. Understanding gas laws is crucial to understanding the physics of scuba diving. The gas laws relative to scuba diving are Boyle's Law, Dalton's Law, Henry's Law and Charles' Law.

  1. Boyle's Law

    • Named after it's discoverer Robert Boyle, Boyle's Law states: As pressure increases, volume decreases. As pressure decreases, volume increases.

      This is relevant to scuba diving in the context of depth and water pressure. Pressure increases with depth, and thus volume will be decreased as a descent is made and will increase upon ascent. This means that every air space on the diver, both dead air space (such as the mask) and live air spaces (such as the lungs), must be paid attention to to avoid problems such as decompression sickness and lung over-expansion injuries. Therefore breathing techniques, equalizing air spaces and never holding your breath are affected by Boyle's law. In addition buoyancy can be affected too, with wetsuit material being compressed and thus becoming less buoyant.

    Dalton's Law

    • John Dalton stated in his law that "the pressure exerted by a mixture of gases is equal to the sum of the pressures that would be exerted by the gases individually". This is relevant to scuba diving with regard to the individual gases in a mix that will compress equally as outside pressure increases.

    Henry's Law

    • Henry's Law, named for William Henry, states that "the mass of a gas which dissolves in a volume of liquid is proportional to the pressure of the gas". This essentially says that as pressure increases then our bodies will absorb more gas. Thus at greater depths the amount of gas absorbed into our body will be greater. This means that deeper dives have to be calculated shorter to allow for this, or risk the possibility of decompression sickness.

    Charles' Law

    • Charles' Law says that cooling a gas decreases the volume of the gas. If the volume does not change then pressure must decrease. This means that if a scuba tank is heated then the pressure will increase, which accounts for accidents that have happened with scuba tanks being left in hot environments.

    Diving

    • The physics of diving take into account all of the laws mentioned in applying relative standards, in order that divers can dive safely with knowledge of the effects of gas laws on their bodies and their dive times. Most dive rules are derived with respect to the gas laws and research continues into their effect on the human body while diving.