Hair incorporates chemical compounds from the bloodstream and external sources as it grows. Different analytical procedures are proposed, but no consensus can be found for external contamination removal (washing stage). Thus, a major limitation of the use of hair analysis for human biomonitoring is the issue related to the washing efficiency, and the objective of this study was to propose a simple washing method for a better cleaning of external contamination. Based on a sequence of three steps of detergent or acid washing (Triton, nitric acid, and hydrochloric acid), the TNCl method was tested on raw and spiked samples and compared to other methods. Thirty-seven inorganic elements were analyzed by inductively Coupled Plasma Mass Spectrometry (ICP-MS) after washing and acid digestion of 10 hair samples (Li, Be, Na, Mg, Al, P, K, Ca, V, Cr, Fe, Mn, Co, N, Cu, Zn, As, Se, Sr, Mo, Ru, Ag, Cd, Sn, Sb, Cs, Ba, La, Ce, Nd, Gd, Lu, Tl, Pb, Bi, Th, and U). The inorganic element concentrations in the hair samples were compared to those reported in the literature. The TNCl method was shown to be more efficient than other methods based on the use of surfactants and organic solvents.