Page 118

19116TC

NAUI Scuba Diver 106 Diving Science long inhalations and long exhalations. This is the best way to breathe under water. Another factor in air consumption is your physical size. Larger people have larger lungs and use more air than smaller people who have smaller lungs and smaller overall metabolic needs. To compensate for these differences, sometimes larger divers will use larger cylinders. There is usually no reason for a small person to carry the same size tank as a larger person unless it is needed for a specific purpose. Body temperature also affects your breathing. The colder you are, the more you breathe. This is unfortunate because heat is also lost each time you exhale. Therefore, you need to be sure to wear the proper amount of insulation for the conditions. Divers who are physically fit breathe less and use their air more efficiently. They also do not have to oxygenate excess body fat. These factors, or combinations of these factors, can significantly affect your breathing rate under different conditions. Through experience, you will learn to estimate the amount of air you will use based on all these factors. Monitoring Air Consumption Most sport divers do not calculate their air consumption before each dive. Instead, as they gain experience diving, they keep a record in their logbooks of how long their air lasts at different depths and in different conditions. This enables them to make rough predictions of the time they will be able to dive at a given depth, based on their air supply. They monitor their submersible pressure gauges, dive timers, and dive computers and use the information from these instruments to determine when to begin their ascent. Even if you calculate your air consumption mathematically, which is possible, any combination of the air consumption factors can change your predicted air consumption rate. If you work harder than planned or the water is colder than you thought, your air consumption rate will be affected. In certain specialty areas of diving, it is essential that you predict your air consumption to avoid running out of air. This is especially important if you participate in deep diving, cave or cavern diving, or wreck diving. Anyone who participates in this type of diving must know how much air they will need for any given dive. Your rate of air consumption will change quite a bit during the first 10 or 20 dives you make. Recording every dive in your logbook will help you to estimate how long your air will last on most dives at different depths. Be sure to record the size of cylinder you use on each dive if you use different size cylinders. This is a good practice to continue even beyond your early dives, because you will learn how much your usual rate is affected by exertion, temperature, and other factors. You will also be able to estimate not only the duration of your air supply for a given depth, but will be able to adjust it for other factors as well. Verify What You Have Learned Review the following questions about air consumption: 14. Two factors that affect your air consumption rate under water are ________________________ and ___________________________. 15. Divers monitor their air supply under water by checking their ___________________________. YOUR BODY When you dive, the pressure of the water affects your air spaces as well as your breathing. How Pressure Affects Your Air Spaces The air spaces in your body include your lungs, sinuses, and middle ears. You can also have air spaces in your stomach, intestines, and teeth (figure 4-20). There are also two air spaces outside your body that you need to consider when diving. Those are your mask and dry suit (if you are wearing one). Pressure can affect these spaces in dramatic ways, called the direct effects of pressure.


19116TC
To see the actual publication please follow the link above