As such, there are no regulations set by a federal body that govern the design, size, or any other specification of a ‘No Spray Zone’ sign. However, you must check with your state’s Department of Agriculture to know if there are any design requirements for the ‘No Spray Zone’ sign or ‘Do Not Spray’ sign. For example - The Minnesota government has 18" x 24" aluminum “Organic Farm - Please Do Not Spray" signs for Minnesota organic farmers.