Scuba divers use two basic types of air tanks. Both types are strapped to the diver’s back and provide clean air for the diver. Open-circuit sets provide an oxygen/nitrogen mix for the diver to inhale, who then exhales it into the water. This type of set is less expensive and is generally used in more shallow dives of less than 100 feet. Open-circuit sets come with one, two, or even three tanks, though sets with one tanks are most common. This type of set also goes by the name aqualung. Divers wearing an open-circuit set can be under water for 30 to 60 minutes, depending on their experience.

Closed-circuit sets, commonly called rebreathers, are used for deeper and longer dives. Rebreathers can allow for up to seven hours of underwater exploration. Rebreathers are designed to capture exhaled air, pass it through a scrubber, and circulate it back to the diver as useable air. How long a diver can stay under water is determined by the life of the scrubber and the water temperature.

Semiclosed rebreather sets allow for two to three times the underwater duration. In these types of sets, gas (air) is recycled but infused with a constant supply of fresh gas. Because some of the gas is recycled, the tanks for these sets are smaller than open-circuit tanks.

About the Author:

Dr. Randy Allan is a primary care physician who makes house calls in the Winnipeg, Canada, area. Dr. Allan enjoys scuba diving with his family in Australia, Belize, Thailand, and Mexico.


Scuba diving is an incredible water sport that my family and I highly recommend to anyone wanting to discover and enjoy the underwater world. Before going under, though, you must understand the basics of gear, breathing, and movement. Scuba diving classes are offered in most diving hotspots around the world, and you must be certified before any diving company will take you out. Your diving instructor will explain each piece of gear you need, where to purchase or rent your gear, and how to use it. This article is a primer to prepare you for your first day of class.

Scuba certification classes take place in a classroom and in water. You will be taught how your body uses air and how to breathe with air tanks. You will learn about air pressure in the tanks and about underwater air pressure and how it affects your body.

To start training, five essential items comprise scuba diving gear: mask, booties, fins, weight belts, and snorkel. These pieces of equipment must be fitted to your body. Each serves an important purpose and is integral to a good diving experience. These items are purchased, not rented. Novice divers can rent wetsuits. However, if you will be diving with any regularity, you will want to purchase your own wetsuit. Divers also generally purchase buoyancy control devices, diving gauges, and scuba regulators, though not until they are nearing certification completion. Air tanks, however, are nearly always rented from a local dive shop. Shops inspect and fill the tanks before and after every use.

To obtain open-water certification, you must be 15 years of age or older. Junior certification is available to those aged 10 to 15. You must be in good health and be able to swim 200 yards and float or tread water for at least 10 minutes. Some diving operations will want to see a doctor’s release if you have health issues like thyroid disease. Diving operators may also not accept people with health issues like asthma, diabetes, and high blood pressure.

About the Author:

Dr. Randy Allan is a primary care physician who practices in the offices of Main Street Medical Clinic in Winnipeg, Canada. Dr. Allan also cares for patients at home, including performing various in-home lab tests. Dr. Allan and his family enjoy diving in locations around the globe including Australia and Thailand.

Before the advent of high-tech equipment, doctors saw many of their patients at home. As technology advanced, physicians discovered they could treat their patients better from a central location with devices that increased their ability to provide care. Today, as physician waiting rooms get fuller, and the time a doctor gets to spend with patients steadily decreases, many doctors and patients desire something better. Enter the rebirth of the house call.

As the rate of growth of the elderly population increases, so too do their needs, and many of the oldest and sickest patients lack the means, or health, to see a doctor in the office. Many of these aged patients end up in the emergency room, which is expensive to an already taxed Medicare system. However, in the United States, Medicare now offers reimbursements to physicians who make house calls, and the Independence at Home Act will encourage more doctors to treat patients at home. In Canada, the government has multiple initiatives for expanding house call services.

Doctors who make house calls get to spend more time with their patients and provide more tailored care. They get to see how their patients live and acquire a better understanding of the obstacles patients may face. Mobile technology also expands the services the in-home doctor can provide, including blood tests, lab draws, and even x-rays and EKGs.

Of the many benefits in-home care provides, one of the most important is the change that occurs in the relationship between physician and patient. The patient-doctor relationship becomes more proactive than reactive when doctors have the time to connect more with the lives of those in their care.

About the Author: Dr. Randy Allan provides in-home care through the Main Street Medical Clinic in Winnipeg, Canada. Dr. Allan established house call procedures at Main Street and Four River Medical Clinic and is the only primary care physician in his area that performs a multitude of in-home lab tests.

Dr. Randy Allan’s Blog

August 10, 2012

Hello and welcome to my blog!