ventilation, and air-conditioning property. (C) Fire protection and alarm systems. (D) Security systems. . (c) Repeal of exclusion for certain property The last sentence of section 179(d)(1) is amended by inserting (other than paragraph (2) thereof) after section 50(b) . (d) Effective date The amendments made by this section shall apply to property placed in service in taxable years beginning after December 31, 2017. B Cost recovery rules 311. 50-percent expensing made permanent (a) In general Section 168(k)(2) is amended to read as follows: (2) Qualified property For purposes of this subsection— (A) In general The term qualified property means property— (i) (I) to which this section applies which has a recovery period of 20 years or less, (II) which is computer software (as defined in section 167(f)(1)(B)) for which a deduction is allowable under section 167(a) without regard to this subsection, (III) which is water utility property, or (IV) which is qualified improvement property, and (ii) the original use of which commences with the taxpayer. (B) Exception for alternative depreciation property The term qualified property shall not include any property to which the alternative depreciation system under subsection (g) applies, determined— (i) without regard to paragraph (7) of subsection (g) (relating to election to have system apply), and (ii) after application of section 280F(b) (relating to listed property with limited business use). (C) Special rules (i) Sale-leasebacks For purposes of clause (ii) and subparagraph (A)(ii), if property is— (I) originally placed in service by a person, and (II) sold and leased back by such person within 3 months after the date such property was originally placed in service, such property shall be treated as originally placed in service not earlier than the date on which such property is used under the leaseback referred to in subclause (II). (ii) Syndication For purposes of subparagraph (A)(ii), if— (I) property is originally placed in service by the lessor of such property,