RCW 70A.15.2500: Investigation of conditions by control officer or department—Entering private, public property.

For the purpose of investigating conditions specific to the control, recovery or release of air contaminants into the atmosphere, a control officer, the department, or their duly authorized representatives, shall have the power to enter at reasonable times upon any private or public property, excepting nonmultiple unit private dwellings housing two families or less. No person shall refuse entry or access to any control officer, the department, or their duly authorized representatives, who requests entry for the purpose of inspection, and who presents appropriate credentials; nor shall any person obstruct, hamper or interfere with any such inspection.