40 CFR § 761.302 - Proportion of the total surface area to sample.
(a) Large nearly flat surfaces. Divide the entire surface into approximately 1 meter square portions and mark the portions so that they are clearly identified. Determine the sample location in each portion as directed in § 761.304.
(1) For large nearly flat surfaces contaminated by a single source of PCBs with a uniform concentration, assign each 1 meter square surface a unique sequential number.
(i) For three or fewer 1 meter square areas, sample all of the areas.
(ii) For four or more 1 meter square areas, use a random number generator or table to select a minimum of 10 percent of the areas from the list, or to select three areas, whichever is more.
(2) For other large nearly flat surfaces, sample all of the one meter square areas.
(b) Small or irregularly shaped surfaces. For small surfaces having irregular contours, such as hand tools, natural gas pipeline valves, and most exterior surfaces of machine tools, sample the entire surface. Any person may select sampling locations for small, nearly flat surfaces in accordance with § 761.308 with the exception that the maximum area in § 761.308(a) is <1 meter square.
(c) Preparation of surfaces. Drain all free-flowing liquids from surfaces and brush off dust or loose grit.