A recertified product is something that was sent back to either the seller (the store that it was bought from) or the producer, and it was fixed (if it was broken) or repackaged (if it was just returned, not broken). Often a recertified product will be without the original warranty (if it is a computer component or some other electronic item).
You can as you also need to take some classes to get recertified even in the same sate.
Hydraulic cylinder use a liquid medium, often some type of viscous oil, in the cylinders and can be subject to higher pressures then pneumatic cylinders which use air or some other gas and work under a lower pressure.
Ambulances carry oxygen cylinders because it is often used to revive people, e.g. For people rescued from drowning or people rescued from smoke filled rooms.Hospitals also use it for patients with breathing difficulties e.g. asthma.
it is a password recovery software often used by hackers
Yes, you do need to be recertified every so often. I would imagine this is to keep up with the emerging technology and updates. http://www.cisco.com/web/learning/le3/learning_about_recertification.html
Recovery from spine surgery is a long and often painful process. Your doctor will prescribe physical therapy to help speed your recovery. Be sure and follow that regimen carefully for the fastest recovery.
Gas cylinders should be re-tested every 5 to 10 years, depending on the type of gas and the regulations in your specific location. It is important to have cylinders inspected regularly to ensure they are safe for use.
10 years
30 days
Twice from Oolga Nelson` Formulae
Gases are typically stored in gas cylinders, which are made of metal and designed to withstand the pressure of the gas inside. These cylinders are sealed to prevent leaks and are often color-coded to indicate the type of gas they contain.