Iowa Code § 89B.14

If a building or structure has a floor space of five thousand square feet or less, an employer shall post signs on the outside of the building or structure identifying the type of each hazardous chemical contained in the building or structure. If the building has more than five thousand square feet, the employer shall post a sign at the place within the building where each hazardous chemical is permanently stored to identify the type of hazardous chemical. If the hazardous chemical or a portion of the hazardous chemical is moved within the building, the employer shall also move the sign or post an additional sign at the location where the hazardous chemical is moved. All letters and figures on signs required by this section shall be at least three inches in height. However, upon the written application of an employer, the division may permit less stringent sign posting requirements. The signs shall comply with the national fire protection association’s standard system for the identification of fire hazards of materials, based upon NFPA 704-1980. The division shall adopt rules exempting employers from the requirements of this section when a building or structure or a portion of a building or structure does not contain significant amounts of a hazardous chemical.

84 Acts, ch 1085, §14C85, §455D.14C87, §89B.14