All VDH regulations must conform with federal regulations. For example, FDA regulation states that the coefficient of variation for radiographic air kerma reproducibility measurements must be no greater than 5% (https://www.ecfr.gov/current/title-21/part-1020/section-1020.31#p-1020.31(b)(1)), but the current VDH regulation specifies 10% (https://law.lis.virginia.gov/admincode/title12/agency5/chapter481/section1621/#:~:text=1.%20Coefficient%20of%20variation.%20For%20any%20specific%20combination%20of%20selected%20technique%20factors%2C%20the%20estimated%20coefficient%20of%20variation%20of%20the%20air%20kerma%20shall%20be%20no%20greater%20than%200.10.), exceeding the federally mandated tolerance limit.