To assess the risk of blood borne pathogen transmission to health care workers (HCWs) via the inhalation of blood aerosols during orthopedic surgery, a study was conducted to characterize the blood aerosols produced during different orthopedic surgical procedures and to determine whether blood aerosols were produced in operating rooms with laminar flow. Surgical procedures included total hip replacement, total knee replacement, vertebral fusion, and hip reconstruction. Aerosol samples were taken using Marple personal cascade impactors, filters, area filter samplers and a quartz crystal microbalance cascade impactor system. The hip replacement surgeries were arbitrarily divided into four stages for sample collection: skin incision, bone cutting, prosthesis installation, and room cleanup. Aerosol samples were taken for ten surgical procedures, and all were found to contain hemoglobin associated particles. Differences in the amount of irrigation and suction between the surgeries were correlated to levels of blood associated aerosols. The authors conclude that blood associated aerosols are produced during orthopedic surgery, and that particle size and concentration is dependent upon the procedure being performed.