Asepsis is the state of being free from disease-causing micro-organisms (such as pathogenic bacteria , viruses , pathogenic fungi , and parasites ). The term often refers to those practices used to promote or induce asepsis in an operative field of surgery or medicine to prevent infection .
The goal of asepsis is to eliminate infection, not to achieve sterility. Ideally, a surgical field is sterile , meaning it is free of all biological contaminants (e.g. fungi, bacteria, viruses), not just those that can cause disease, putrefaction , or fermentation . At present, there is no method to safely eliminate all of a patient's contaminants without causing significant tissue damage.
The modern concept of asepsis evolved in the 19th century. Ignaz Semmelweis showed that washing hands prior to delivery reduced puerperal fever . After the suggestion by Louis Pasteur , Joseph Lister, 1st Baron Lister introduced the use of carbolic acid as an antiseptic, and in doing so, reduced surgical infection rates. Lawson Tait went from antisepsis to asepsis, introducing principles and the iconic statutes that have remained valid to this day. Ernst von Bergmann introduced the autoclave , a device used for the practice of the sterilization of surgical instruments. 
Asepsis refers to a procedure that is performed under sterile conditions. This includes medical and laboratory techniques (such as with bacterial cultures ). This can incorporate techniques such as flame sterilization and methods to protect wounds and other susceptible sites from organisms that could cause infection. This can ensure that only sterile equipment and fluids are used during invasive medical and nursing procedures. The largest example of aseptic techniques is in hospital operating theatres where the aim is to keep patients free from hospital micro-organisms (Crow 1989).
Ayliffe et al. (2000) suggests that there are two types of asepsis--medical and surgical. Medical or clean asepsis reduces the number of organisms and prevents their spread; surgical or sterile asepsis includes procedures to eliminate micro-organisms from an area and is practiced by surgical technologists and nurses in operating theaters and treatment areas.
In an operating room, while all members of the surgical team should demonstrate good aseptic technique, it is the role of the scrub nurse or surgical technologist to set up and maintain the sterile field.   Medical procedure rooms should be laid out according to guidelines including regulations concerning filtering and airflow . Members of the surgical teams may wash their hands and arms with germicidal solution (e.g. an iodine solution such as betadine ), and may also wear sterile gloves and gowns. Staff members' hair should be covered and surgical masks should be worn. Instruments should be sterilized through autoclaving or by using disposable equipment. Suture material or xenografts also need to be sterilized beforehand. Dressing material should be sterile. Antibiotics may also be used, and dirty, biologically contaminated material should be subject to regulated disposal.