The hydro testing diving cylinder should be carried out in accordance with local laws and regulations or if the cylinder has been damaged, heat treated or has any external damage that can affect the cylinders integrity.
As listed under table 3 of your RDP or on the inside lid of the PADI eRDPml are the rules for dealing with emergency decompression.
If a diver accidentally exceeds their NDL by no more than 5 minutes the following applies.
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.
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.
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.