Table 10-4.—Micro-organisms and Levels of Disinfection for that particular product. The following are some of the criteria for effective chemical disinfection: The degree of microbial kill or deactivation required The composition and texture of the item being treated The technical requirement and ease of use of the available  agents Regardless of the product selected, there is no single chemical or heat agent available today that will meet  all  these  criteria.  As  always,  follow  label directions  precisely.  Give  strict  attention  to  the proper use of the product regarding mixing, dilution, method and duration of the application, temperature requirements, shelf-life, and if applicable, reuse life. Organic Debris Present Blood, saliva, and other organic material may contribute to the failure of a germicidal process by either direct inactivation of the disinfectant or the actual   layering   of   the   micro-organisms   on   the instruments   or   equipment,   thereby   preventing penetration of the germicide. LEVELS  OF  DISINFECTION Type and Concentration of the Germicide The   EPA   classifies   disinfectants   as   high, intermediate, or low level, based on the effectiveness and contact time of the solution and the biocidal activity  of  an  agent  against  bacterial  spores, mycobacterium  tuberculosis,  lipid  and  nonlipid viruses, and vegetative bacteria. Table 10-4 describes the   level   of   disinfection   required   to   kill   the micro-organism  named. Generally, when all other variables are constant, the higher concentrations of a chemical agent are more effective and require a shorter time to disinfect. Use of   dilutions   other   than   those   specified   by   the manufacturer  adversely  affect  some  intermediate- level  disinfectants,  specifically  iodophors.  In  all instances,  follow  the  manufacturer’s  recommendations. GENERAL CATEGORIES OF LIQUID CHEMICAL AGENTS FACTORS INFLUENCING GERMICIDAL PROCEDURES A large variety of liquid disinfectants are available today, and it is probable that many new ones will become  available  in  the  future.  When  selecting  a product,  make  sure  that  the  label  has  an  EPA registration number on it. Table 10-15, is a guide to chemical  agents  for  disinfection  and  sterilization. Since they may be subject to change, be sure to read the manufacturer’s instructions before using. Next, we will discuss the four most commonly used chemical agents, glutaraldehyde and chlorine dioxide based solutions, iodophors, and phenolics. The  factors  associated  with  the  micro-organisms, as  well  as  those  associated  with  the  surrounding physical and chemical environment, influence the antimicrobial efficiency of the germicides. They are described next. Bioburden 10-18 Nature of the Material The  easiest  surface  to  disinfect  is  a  smooth, nonporous, and cleanable one. If the materials are incompatible with disinfectant, damage and corrosion can occur. Glutaraldehyde-Based  Solutions These agents are available in several formulations differing in pH, concentration, use in dilution, and exposure  time.  They  are  classified  as  high-level disinfectants  or  sterilants. Always wear impermeable gloves and protective eyewear  when  handling  these  solutions.  Irritation  of the hands is common and personnel are always at risk of  splashes  occurring  whenever  liquids  are  being Under a given set of circumstances, the higher the level  of  microbial  contamination,  the  longer  the required  exposure  to  the  disinfectant  is  needed. Additionally,   resistant   micro-organisms   require longer exposure times. Level of Bacterial Bacterial   Tubercle   Nonlipid Lipid Vegetative Activity Spores Bacillus Viruses Viruses Bacteria High Maybe Yes Yes Yes Yes Intermediate No Yes Yes Yes Yes Low No No No Yes Yes In the absence of gross organic contamination.