The activities, findings, and recommendations associated with the air sampling aspects of a NIOSH Health Hazard Evaluation conducted at two facilities of a large midwestern greenhouse company were reported. The company produced several floriculture and nursery products including bedding, seasonal and ornamental plants, and foliage. The presence of pesticides in the work environment was evaluated by area air sampling for 3 to 4 consecutive days after spraying and cold fogging applications. Personal breathing zone air sampling of the applicator during a spraying application of diazinon (333415) resulted in the measurement of high concentrations during a brief application period of 40 minutes. Safety recommendations cited include: each applicator at the greenhouse company should continue to wear a hooded disposable protective suit, industrial grade latex gloves, rubber boots, and a NIOSH approved full facepiece respirator with pesticide cartridges while applying these types of pesticides. Night watchmen or any other workers who enter a treated section during a restricted entry interval should also wear such equipment. After every application the applicator's disposable protective suit, gloves, and respirator cartridges should be placed in a garbage bag, sealed and stored for subsequent disposal to a landfill.