Aseptic Technique, Sterile Technique & Equipment Disinfection

Medical Asepsis vs. Surgical Asepsis

Infection-control technique operates at two distinct levels, and the exam expects a CPCT/A to know exactly which one a given task requires.

Medical asepsis ("clean technique") reduces the number and spread of microorganisms — it does not eliminate them. Handwashing, wearing clean (non-sterile) gloves for routine care, and standard cleaning of patient-care surfaces are all medical asepsis. It is used for most everyday patient-care tasks: bathing, feeding, taking vital signs, and changing linens.

Surgical asepsis ("sterile technique") eliminates all microorganisms, including bacterial spores, from an object or area. It is required for any invasive procedure that breaches the skin or enters a normally sterile body cavity — inserting a urinary catheter, performing a sterile dressing change, or assisting with a minor procedure.

The Sterile Field: Core Rules

Once a sterile field is opened, it must be actively protected from contamination for the entire procedure. Key rules:

• The outer 1-inch border of a sterile drape is considered contaminated the moment it is opened — nothing sterile may be placed within that border.
• Never turn your back on a sterile field, and never leave it unattended; a field that goes unmonitored, even briefly, is considered contaminated.
• Anything below waist level or out of direct line of sight is contaminated, even if it was sterile a moment earlier.
• Sterile touches sterile only — a sterile-gloved hand or sterile instrument that contacts anything non-sterile (skin, an unsterile surface, the outside of a wrapper) is immediately contaminated and must be replaced.
• Reaching over a sterile field with a non-sterile arm or object contaminates the field, even without direct contact, because of airborne particles and gravity.
• A sterile field that becomes wet from spilled or splashed liquid (strike-through) is considered contaminated.
• Sterile packages are opened facing away from the body and set down so the inner sterile surface faces up; the outside of any wrapper is always treated as non-sterile.
• Talking, coughing, or sneezing directly over an open sterile field can contaminate it with respiratory droplets, which is one reason a mask is worn for many sterile procedures.

Levels of Decontamination

Three progressively stronger levels of decontamination are tested, and confusing them is a common exam trap:

Items that will be sterilized are typically wrapped or pouched and run through the process with a chemical or biological indicator so staff can confirm sterility was actually achieved before the item is used on a patient. Cleaning must always occur before disinfection or sterilization — visible organic matter (blood, tissue, dried body fluid) blocks a disinfectant or sterilant from reaching the microorganisms underneath it.

Disinfectant Contact and Dry Times

A disinfectant only works if it stays wet on the surface for the full contact (dwell) time printed on the manufacturer's label — wiping a surface dry before that time elapses does not achieve the labeled level of disinfection, no matter how thoroughly the surface was wiped.

• Bleach (sodium hypochlorite): A 1:10 dilution (1 part household bleach to 9 parts water, mixed fresh) is commonly used against C. difficile spores and other resistant organisms. Contact time varies by product and soil level and can run up to 10 minutes; always follow the manufacturer's stated contact time rather than an assumed one.
• Alcohol (70–90% isopropyl or ethyl): An intermediate-level disinfectant that evaporates quickly, so the surface must be kept visibly wet for the label's stated time; alcohol is not sporicidal and will not reliably kill C. difficile spores.
• Quaternary ammonium compounds ("quats"): Common low-to-intermediate-level environmental surface disinfectants; effective against many bacteria and enveloped viruses but require a label-specified wet-contact time (often several minutes) and are generally not sporicidal.

Because product formulations and contact times vary by manufacturer, the CPCT/A's rule is constant: read and follow the product label for dilution, contact time, and any required rinse step, and never substitute a faster-drying product when a longer sporicidal contact time is required, such as for C. diff or norovirus.

Using the wrong level of technique in either direction causes real problems: applying only medical asepsis to an invasive procedure introduces pathogens directly into a sterile body site, while treating every routine task as if it required surgical asepsis wastes sterile supplies and time without adding any real protection. Matching the level of technique to the task — clean for routine care, sterile for invasive procedures, and the correctly timed disinfectant level for the surface or equipment involved — is the underlying skill this section tests.