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.

LEVELS OF DISINFECTION

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.

FACTORS INFLUENCING GERMICIDAL PROCEDURES

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.

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.

Bioburden

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.

Table 10-4. - Micro-organisms and Levels of Disinfection

In the absence of gross organic contamination.

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.

Type and Concentration of the Germicide

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

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.

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