The term "personal property" for the purposes of this chapter shall include every form of tangible personal property, including but not limited to, all goods, chattels, stock in trade, estates, or crops: PROVIDED, That all personal property not assessed and subjected to ad valorem taxation under Title 84 RCW, all property under contract or for which the district is receiving payment for as authorized by RCW 52.30.020 and all property subject to the provisions of chapter 54.28 RCW, or all property that is subject to a contract for services with a fire protection district, shall be exempt from the benefit charge imposed under this chapter: PROVIDED FURTHER, That the term "personal property" shall not include any personal property used for farming, field crops, farm equipment or livestock: AND PROVIDED FURTHER, That the term "improvements to real property" shall not include permanent growing crops, field improvements installed for the purpose of aiding the growth of permanent crops, or other field improvements normally not subject to damage by fire.