Add inhibitor to achieve final concentration of 1U/ul in your reaction. During assembly of a reaction, RNase Inhibitor should be added before other components that are a possible source of RNase contamination (i.e. enzymes, plasmid from a mini prep.)
*RNase Inhibitor is a 50 kDa protein that will be inactivated in denaturing conditions.
**RNase Inhibitor should be used below 50°C.