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The steady-state concentration of a contaminant in a well-mixed space is described by the mass-balance relationship C = G/Q, where G is the constant generation rate (mass per time) and Q is the effective removal rate via ventilation (volume per time multiplied by mixing efficiency). When ventilation doubles, Q doubles, causing C to decrease proportionally, assuming generation and other losses remain constant. Boyle’s law (Option A) relates gas volume and pressure at constant temperature and is unrelated to contaminant removal dynamics. Dalton’s law (Option B) addresses the additive nature of partial pressures in mixtures but does not govern removal kinetics. Henry’s law (Option D) describes gas-liquid partitioning, relevant for scrubbers or dissolved gases, not bulk room dilution alone. The first-order mass balance model also accommodates additional sinks such as deposition or reaction by incorporating loss terms; however, in many IH applications, ventilation dominates. This conceptual framework underpins dilution ventilation design, contaminant control strategies, and interpretation of general exhaust effectiveness across industrial and construction environments.