Washington Revised Code Title 18. Businesses and Professions § 18.160.100. Unlicensed operations--Penalty

Any fire protection sprinkler system contractor who constructs, installs, or maintains a fire protection sprinkler system in any occupancy, except an owner-occupied single-family dwelling, without first obtaining a fire sprinkler contractor's license from the state of Washington, is guilty of a gross misdemeanor. This section may not be construed to create any criminal liability for a prime contractor or an owner of an occupancy unless it is proved that the prime contractor or owner had actual knowledge of an illegal construction, installation, or maintenance of a fire protection sprinkler system by a fire protection sprinkler system contractor.