Carbon Monoxide poisoning, although difficult to get with modern compressor technology is something divers must be aware of.

CO2 is odorless and tasteless so recognition of signs and symptoms is imperative. 

Red nails and lips are difficult to see while underwater due to light absorption but other symptoms such as dizziness, headache, and vomiting while diving should always prompt the end of a dive and testing of air quality as a precaution if red lips and nails are present once surfaced. 

As the temperature of a gas begins to increase the molecules will begin to expand. If this occurs in a diving cylinder the pressure exerted against the internal walls will increase.

Because the cylinder is an inflexible container it will appear as a rise in the internal pressure of the tank.

A good rule of thumb if filling a cylinder or diving in cold environments is that every +/- 1 degree C will transfer to approximately 0.6 Bar pressure change within the cylinder. 

Any time someone has aspirated water there is a risk that the function of lungs has been compromised and a risk of infection from bacteria in the water. This is very difficult to determine as a lay first aider and via a visual analysis. 

Medical assistance should always be sought after anyone has experienced any degree of drowning. PADI amended the terminology used when teaching EFR and Rescue Diver programs to reflect this.

Near Drowning is no longer used to reduce instances when a rescuer may assist someone that has aspirated water to any degree. They are now considered to have had a drowning incident and must seek medical assistance. 

An extremely popular acquisition program for young divers, especially in the holiday environment where shallow dives are readily available. Each section of the basic programs that all OWSI's can teach are found in the PADI Instructor Manual - section one being the program standards. 

Information about minimum ages can be found either here or in Key Standards for quick reference.

Open Circuit is popular because of its simple design and relatively low-cost build and maintenance. While using air on this system it makes scuba diving accessible to most people in many environments.

Closed Circuit systems are becoming more and more popular and simpler to use thus gaining popularity. This also allows more affordable and safer exploration into new environments such as caves, wreck, and mines.

I know it's on my bucket list. And you?