The third key component of the generator definition is the phrase "act or process." Because a generator is defined as the person whose act or process first causes a hazardous waste to become subject to regulation, sometimes the generator of a waste may not necessarily be the person who actually produced the waste. For example, if a cleaning service removes residues from a product storage tank excluded in §261.4(c), the person removing the residues is the first person to cause the waste to become subject to regulation, not the owner of the tank (i.e., the person who produced the waste).