Emission Characteristics of VOCs from Lubricant Oils Widely Used in Industrial Buildings by a Dynamic Headspace Sampling Method

Lubricant oils emit strongly volatile organic compounds (VOCs) in industrial settings. The oil–gas interface concentration is a key parameter to drive the emission process. In this study, a dynamic headspace sampling method was proposed to characterize the interface concentration with the advantage of being simple and low cost. A critical sampling flow rate was theoretically derived as DA/L, where D (m2/s) is the diffusion coefficient of VOCs in the air, A (m2) is the surface area of the oil–gas interface, and L (m) is the height of the headspace. Experimental results prove that oil–gas equilibrium can be readily maintained by a sampling flow rate lower than the critical one. Four lubricant oils were characterized by the proposed method. The results indicate that the top five species accounted for 64–85% of the total VOC concentrations. Butylhydroxytoluene, an antioxidant additive, is the only compound among the top five species for all four lubricant oils. A V-shaped volatility distribution pattern was consistently observed. The vaporization enthalpies of VOCs for lubricant oils are smaller than those for pure substances, indicating weaker molecular interactions. The method offers a new powerful tool to characterize VOC pollution and consequently prioritize source control.