This study was designed to determine e-liquid constituents in the atmosphere where e-vapor products are used. The objective was to measure levels of nicotine, propylene glycol (PG), glycerol, menthol and suspended particulate in a room where e-vapor prototypes/MarkTenTM commercial products were being evaluated. The room space was 4892 ft³ and had 1.47 air changes/ hour. There were four test days and each test day comprised six separate vaping sessions. Each session consisted of 3-12 participants with a total of 183 participants over four test days. Each participant was instructed to take 6 puffs ad libitum. Baseline measurements were collected at the beginning and end of the four test day period. Active samples were collected over the 12-hr. test period for the selected constituents and total suspended particulate (TSP) using NIOSH methods. Direct reading measurements were collected over the 12-hr. test period for nicotine, menthol, and suspended particulates using a portable GC and condensation nuclei counter, respectively. Detection limits were 0.015 mg/m³ (nicotine), 0.065 mg/m³ (PG), 0.077 mg/m³ (glycerol), 0.18 mg/m³ (menthol), and 0.153 mg/m³ (TSP). Regulatory exposure limits (NIOSH), calculated for 12-hour periods, are 0.25 mg/m³ (nicotine), 5 mg/m³ (PG, glycerol and TSPs) and 4.8 mg/m³ (menthol). Direct reading results were 0.0-0.01 mg/m³ (nicotine), 0-0.3 mg/m³ (menthol) and 2767-169370 particles/cm³ (particle diameter ranging from 20-1000 nm). The particle count correlated with product use in the rooms. In conclusion, room levels of selected constituents were all below applicable regulatory limits and below limits of detection. These findings along with other published literature, should inform a science-based regulatory decision regarding restricting use of e-vapor products.