Answer to Question 1
Fire, or combustion, is a chemical reaction between oxygen and a combustible fuel. Combustion is the process by which fire converts fuel and oxygen into energy, usually in the form of heat. By-products of combustion include light and smoke. For the reaction to start, a source of ignition such as a spark or open flame or a sufficiently high temperature is needed.
Answer to Question 2
When a powder-actuated tool misfires, it should be held in the operating position for a full 30 seconds. At this point it should be fire again. If the tool still misfires it should be held in the operating position for another 30 seconds and then unjammed according to the manufacturer's specifications.