It is well known that in a natural accidental wound or surgical wound, sepsis can occur on contact with contaminated materials including water. Nature contains infinite varieties of microbial organisms, broad classification being fungi, bacteria, viruses and spore-bearing organisms like tetanus. Host immune system and virulence of given species of microbes will determine the severity of infection. In any case surgical sepsis has to be avoided at all costs because of high mutability and or mobility of infection takes place. In case of Orthopaedic and Ophthalmology it may mean total loss of joint or eye. Fortunately most of the pathogenic organisms (not all organisms are pathogenic) are easy to kill outside the body. Once inside the body, microbial resistance to antibiotics, host mechanisms etc. restrict use of powerful physical agents that can be applied out of body.

During any surgery, minor or major, severing of skin and other tissues is necessary. This opens up the natural defense of the body. Sepsis can occur through surgical instruments, gloves, gauge pieces, implants, foreign bodies etc. Proper sterilization of all instruments therefore is mandatory. Apart from instruments and implants that directly come in contact with surgical wound, operation area atmosphere is equally important. Hence the emphasis on fumigation. Formaldehyde has been the most widely used fumigant since considerably long period and proved to be an excellent lethal agent to most of the pathogens, AIDS virus, fungi and spore-bearers. To achieve this the following concentration for volume fumigation is necessary: