Iowa Code § 904.814
There is established in the treasury of the state a permanent adult correctional institutions inmate allowance supplement revolving fund, consisting solely of money paid as board and maintenance by inmates working in Iowa state industries, or working pursuant to section 904.809. The fund established by this section may be used to supplement the allowances of inmates who perform other institutional work within and about the adult correctional institutions including those who are working in Iowa state industries. Payments made from the fund shall supplement and not replace all or any part of the allowances otherwise received by, and shall be equably distributed among such inmates. The work of inmates in other institutional or industry work shall, to the greatest extent feasible, be in accord with the intent stated in section 904.801. The fund may also be used to supplement other rehabilitation activities within the adult correctional institutions. Determination of the use of the funds is the responsibility of the state director who shall first seek the advice of the prison industries advisory board.
Iowa Code § 904.814