Va. Code § 44-157
Whenever all or any part of the regular fire-fighting forces of any county, city or town in the Commonwealth are engaged in rendering aid and assistance, pursuant to this chapter, substitute fire fighters, not exceeding the number of regular fire fighters engaged in rendering such aid and assistance, may be appointed in the same manner as provided by law for the appointment of such regular fire fighters. Except in the case of a volunteer fire company, the compensation of such substitute fire fighters shall be fixed at a sum not greater than the lowest rate of pay for a regular fire fighter in such fire department, company or fire-fighting force. Each person appointed under this section shall be vested with the same powers and charged with the same duties as if he were a regular member of such fire department, company or fire-fighting force. No appointment under this section shall continue for more than two days after the regular fire fighters for whom they are substituting have returned to duty. The compensation of any substitute fire fighter appointed pursuant to this section and any allowable expense actually and necessarily incurred by him in the performance of his duties shall be charged against the county, city or town in and for which he was appointed and shall be audited and allowed in the same manner as other charges against the county, city or town are audited and allowed.
Va. Code § 44-157