(b) Except as provided in subdivision (c), a district shall require an agricultural source of air pollution to obtain a permit unless it makes all of the following findings in a public hearing:

1. (1) The source is subject to a permit requirement pursuant to Section 40724.6.
2. (2) A permit is not necessary to impose or enforce reductions of emissions of air pollutants that the district shows cause or contribute to the violation of a state or federal ambient air quality standard.
3. (3) The requirement for the source or category of sources to obtain a permit would impose a burden on those sources that is significantly more burdensome than permits required for other similar sources of air pollution.

(c) Prior to requiring a permit for an agricultural source of air pollution with actual emissions that are less than one-half of any applicable emissions threshold for a major source in the district for any air contaminant, but excluding fugitive dust, a district shall, in a public hearing, make all of the following findings:

1. (1) The source is not subject to a permit requirement pursuant to Section 40724.6.
2. (2) A permit is necessary to impose or enforce reductions of emissions of air pollutants that the district shows cause or contribute to a violation of a state or federal ambient air quality standard.
3. (3) The requirement for a source or category of sources to obtain a permit would not impose a burden on those sources that is significantly more burdensome than permits required for other similar sources of air pollution.