NIOSH has found evidence of interstitial lung disease among workers exposed to nylon flock (flock workers’ lung) in various plants in the past. In November 2003, based on health complaints among several workers, employees from Hallmark Cards, Inc. requested a health hazard evaluation (HHE) to get a better understanding of the potential respiratory hazards associated with the use of rayon flock at this card-producing plant. In order to characterize exposures, symptoms, and lung function of flock-exposed workers and appropriate internal comparison groups, NIOSH conducted environmental and medical surveys at this plant. The environmental survey consisted of time-integrated sampling, including air samples for gravimetric concentration of respirable dust with side-by-side air samples for fiber concentration. We conducted real-time sampling with aerosol photometers to obtain real-time continuous relative levels of dust (approximately respirable) during some plant activities together with video taping, to record events that might be associated with any observed peaks in real-time readings. For the cross-sectional medical survey, we invited 284 employees, divided into three groups according to their potential exposure, as follows: Group A, workers exposed to flock and paper dust; Group B, workers exposed to paper dust only; and Group C, workers from the ribbon production areas (without significant flock or paper dust exposure). Trained NIOSH interviewers administered computer-based questionnaires that focused on respiratory symptoms, systemic symptoms, physician diagnosis of respiratory illnesses, smoking, work history, respirator use, and whether fit-testing had been conducted. Each participant, unless medically contraindicated, was offered spirometry testing, carbon monoxide diffusing capacity (DLCO) testing, and either a bronchodilator test or a methacholine challenge test (MCT). The 8-hour time-weighted average airborne respirable dust and fiber concentrations were largely below or near the minimum detectable concentrations of 0.03 milligrams per cubic meter of air (mg/m3) and 0.01 fibers per cubic centimeter (fibers/cc), respectively. Peak exposures to airborne particulate occurred during cleaning with compressed air and vacuuming with a compressed-air vacuum. Production-related sources of airborne particulate included the open top of a flock line cyclone, flock module card feed and discharge points, and small foil compressed-air card separators. A total of 239 employees (participation rate = 84%) participated in the medical survey. The employees were predominantly female (54%), white (80%), and never-smokers (55%). Nearly one-half of the employees had worked over 20 years at the Hallmark plant. A total of 146 participants (61%) reported working at least one hour per week in an area where flock-coated cards are processed. A total of 47 participants (20%) reported cleaning with compressed air for at least one hour per week. Overall, 41 workers (17%) reported wearing air-purifying respirators at the plant. Use of respirators while cleaning equipment with compressed air was reported by 26 participants; none of the 26 reported that they had been fit-tested. Use of respirators at other times besides cleaning was reported by 31 workers, only one of whom reported having been fit-tested. Nasal irritation, sinus problems, and eye irritation were the most frequently recorded symptoms. In general, flock workers had higher prevalences of symptoms arising during employment at Hallmark than non-flock workers with paper dust exposures and ribbon workers. Workers who cleaned for one hour or more per week using compressed air generally had higher symptom prevalences than other workers. Working in areas where flock-coated cards are processed and cleaning equipment with compressed air were both significantly associated with the development of nasal symptoms after hire at Hallmark. Cleaning with compressed air was also significantly associated with the development of chronic cough. Spirometry tests showed that male flock workers were significantly more likely than male nonflock workers to have results indicating restrictive lung disease (low forced vital capacity), in which the lungs cannot expand normally. Also, employees who worked a higher number of years in areas where flock-coated cards are processed were more likely to have test findings of decreased volume in the air sacs (decreased alveolar volume) and decreased ability of the lung to transfer gases (low carbon monoxide diffusion capacity). This pattern of changes is not diagnostic by itself, but can indicate scarring and stiffness of the lung tissue which is found in interstitial lung disease (ILD), including "flock workers’ lung". We conclude that working with flock and cleaning with compressed air were associated with health effects in workers at this plant. We recommend that the company take steps to prevent flock-associated dust exposures: by controlling the airborne particulate generated in compressed air cleaning and vacuuming, in the separation of cards at small foil machines processing flocked cards, and at card feed and discharge points at flock lines; by reducing the need to reach into modules; by capturing the opentop cyclone discharge, and by requiring that employees use vacuuming rather than compressed air to remove dust from their clothes. Since safe levels of flock-associated dust are unknown, we recommend that a written respiratory protection program be developed that requires NIOSH certified respirators for compressed air cleaning and fit testing of all respirator users. We recommend informing employees about work-related disease observed among flock workers and providing informational materials to them to share during any physician consultation about concerns or actual health problems. NIOSH investigators determined that a health hazard exists from occupational exposure to flock-associated dust at this plant. This risk is evidenced by upper and lower respiratory symptoms, such as nasal irritation and cough, and objective measurements of lung function suggesting a restrictive pattern, compatible with subclinical interstitial lung disease. These health outcomes are associated with work in areas where flock-coated cards are processed and equipment is cleaned with compressed air.