49 CFR 172.704 (a):

The Department of Transportation (49 CFR 172.704) makes General Hazard Awareness training  mandatory for almost anyone who handles hazardous materials, regardless of the amount. This affects employees who select or fill hazardous materials packages, label containers, complete shipping papers, load or unload vehicles, transport hazardous materials, or operate vehicles used in the transport of hazardous materials. This course meets both your initial and recurrent training requirements.

• (a)(1): Each hazmat employee shall receive general awareness/familiarization training designed to provide familiarity with the requirements of this subchapter, and to enable the employee to recognize and identify hazardous materials consistent with the hazard communication standards of this subchapter.
• (a)(2): Each hazmat employee shall receive function-specific training concerning requirements of this subchapter, or exemptions issued under subchapter A of this chapter, which are specifically applicable to the functions the employee performs.
• (a)(3): Each hazmat employee shall receive safety training concerning – ( i ) Emergency response information required by subpart G of part 172; ( ii ) Measures to protect the employee from the hazards associated with hazardous materials to which they may be exposed in the work place, including specific measures the hazmat employer has implemented to protect employees from exposure; and ( iii ) Methods and procedures for avoiding accidents, such as the proper procedures for handling packages containing hazardous materials.
• (a)(4): Security awareness training. No later than the date of the first scheduled recurrent training after March 25, 2003, and in no case later than March 24, 2006, each hazmat employee must receive General Hazard Awareness training that provides an awareness of security risks associated with hazardous materials transportation and methods designed to enhance transportation security. This training must also include a component covering how to recognize and respond to possible security threats. After March 25, 2003, new hazmat employees must receive the security awareness training required by this paragraph within 90 days after employment.

49 CFR 172.704 (c):

• (c)(1): Initial training:  A new hazmat employee, or a hazmat employee who changes job functions may perform those functions prior to the completion of training provided — (i) The employee performs those functions under the direct supervision of a properly trained and knowledgeable hazmat employee; and (ii) The training is completed within 90 days after employment or a change in job function.
• (c)(2): Recurrent training: A hazmat employee shall receive the training required by this subpart at least once every three years.