The VOC methods are all run using the purge-and-trap (P&T) sample introduction technique; headspace is not allowed for drinking water or wastewater compliance testing in the US. The required US EPA methods for VOCs are US EPA Methods 524.2, 524.3, and 524.4 (Drinking Water), Method 624 (Waste Water), and Method 8260 (Groundwater and Solid Waste).