Figure 3: Bronchoprovocation challenge testing for occupational asthma for the same patient as depicted in Figure 2. The decrease in forced expiratory volume in 1 second (FEV1) after a 30-minute exposure to toluene diisocyanate (TDI; day B, October 27; rectangles) but not after a 30-minute control exposure to paint thinner (day A, October 21; triangles) indicates a positive result on this specific challenge test, providing further confirmation of the diagnosis of occupational asthma due to toluene diisocyanate. Testing was performed in a single-blind manner, with multiple spirometry measurements over time before and after exposure. For day A, FEV1 = 4.17 L, PC20 (concentration of the provoking agent that causes the FEV1 to drop by 20%) = 1.4. For day B, FEV1 = 4.16 L, PC20 = 0.66. Arrow indicates use of reliever medication (salbutamol). Reproduced courtesy of Dr. André Cartier and Medical Resource Communications. 47