Spaulding Classification and the Basics of Cleaning, Disinfection, and Sterilization

Hospital biomedical engineers, sterile processing technicians, and importers of used medical equipment all rely on one foundational framework to decide how a device must be reprocessed between patients: the Spaulding classification. Developed by Dr. Earle Spaulding in 1939 and adopted by the U.S. Centers for Disease Control and Prevention (CDC), this system sorts patient-care items into three risk categories and matches each to a minimum required level of microbial reduction (CDC, A Rational Approach to Disinfection and Sterilization). For organizations that source, refurbish, and export used hospital equipment, understanding this framework is essential — it determines what reprocessing capability a device needs at its destination and what claims can legitimately be made about a unit's condition on arrival.

This article summarizes the Spaulding categories, clarifies the difference between cleaning, disinfection, and sterilization, and reviews chemical compatibility considerations that affect device longevity and safety.

The Three Spaulding Categories

The CDC's Guideline for Disinfection and Sterilization in Healthcare Facilities organizes reusable items by the degree of infection risk associated with their intended use (CDC Guideline for Disinfection and Sterilization).

(Table adapted from CDC Rational Approach to Disinfection and Sterilization and Public Health Ontario's Spaulding classification summary.)

A key nuance for importers and biomedical teams: the classification is based on the item's intended use, not on the device type alone. A vaginal or transrectal ultrasound probe without a barrier cover is semicritical because it directly contacts mucous membranes; the CDC guidance specifically notes that because probe covers can fail, the probe itself must still receive high-level disinfection even when a single-use cover is used (CDC, Disinfection of Healthcare Equipment). The same logic applies to any multi-use device: reclassify by function, not by name.

Cleaning vs. Disinfection vs. Sterilization

These three terms are often used loosely in the field but have distinct, non-interchangeable meanings.

• Cleaning is the physical removal of organic material (blood, tissue, gel, dust) and other soil from a surface using water, detergent, and mechanical action. Cleaning does not necessarily kill microorganisms, but it is a mandatory first step — disinfectants and sterilants cannot penetrate residual soil and organic debris reliably. The CDC states plainly that "cleaning should always precede high-level disinfection and sterilization" (Rutala & Weber, PMC7134755).
• Disinfection uses chemical or thermal means to eliminate most or all pathogenic microorganisms on inanimate surfaces, with three sub-levels:
  • Low-level disinfection (LLD) kills most vegetative bacteria, some fungi, and some viruses, but not mycobacteria or spores. Appropriate for noncritical items such as stethoscopes and BP cuffs.
  • Intermediate-level disinfection inactivates mycobacteria, vegetative bacteria, most viruses, and most fungi but not bacterial spores.
  • High-level disinfection (HLD) destroys all microorganisms except large numbers of bacterial spores, and is the minimum standard for semicritical devices (CDC Guideline for Disinfection and Sterilization).
• Sterilization is a validated process that renders an item free of all viable microorganisms, including bacterial spores. It is required for all critical items, achieved through steam autoclaving (preferred when heat-tolerant), ethylene oxide (EtO), hydrogen peroxide gas plasma, or liquid chemical sterilants for heat-sensitive devices (CDC Rational Approach).

Quick-Reference Checklist: Choosing the Right Process

• Identify the device's intended clinical contact (sterile tissue, mucous membrane, or intact skin only)
• Confirm the Spaulding category based on that contact — not on the device's general type
• Clean thoroughly first, removing all visible soil, before any disinfection or sterilization step
• Match the disinfection/sterilization method to the category (sterilization for critical, HLD minimum for semicritical, LLD for noncritical)
• Verify compatibility of the chosen chemical or thermal method with the specific device model per the manufacturer's Instructions for Use (IFU)
• Document the method, product/lot, contact time, and outcome for every reprocessing cycle

FDA-Cleared High-Level Disinfectants and Sterilants

The FDA maintains a list of cleared liquid chemical sterilants and high-level disinfectants for reprocessing reusable semicritical and critical devices, including glutaraldehyde, hydrogen peroxide, ortho-phthalaldehyde (OPA), and peracetic acid/hydrogen peroxide combinations (FDA, Sterilants and Disinfectants for Processing Reusable Devices). Exposure times for most high-level disinfectants range from roughly 8 to 45 minutes at 20–25°C, depending on the specific chemistry and manufacturer instructions (Rutala & Weber, PMC7134755). For low- and intermediate-level disinfection of noncritical surfaces and equipment, facilities should select products from the EPA's registered disinfectant lists (EPA, Selected EPA-Registered Disinfectants) rather than relying on general-purpose cleaners.

Chemical Compatibility: Protecting the Device While Disinfecting It

Selecting an effective germicide is only half the job — the chemical must also be compatible with the specific device's materials over repeated use. The CDC guideline is explicit: "When a disinfectant is selected for use with certain patient-care items, the chemical compatibility after extended use with the items to be disinfected also must be considered" (CDC Rational Approach).

For biomedical teams and importers handling used equipment, chemical incompatibility is a leading cause of premature device failure and cosmetic or functional damage, particularly for:

• Ultrasound transducers and endoscopes, where incompatible disinfectants can degrade lens coatings, adhesives, and cable jacketing.
• Metal instruments, which can corrode or pit when exposed to chlorine-based agents outside their validated concentration or contact time.
• Plastics and elastomers, which may swell, crack, or discolor with repeated exposure to alcohol- or aldehyde-based products.

AAMI's technical guidance on sterilization compatibility (AAMI TIR17, Compatibility of Materials Subject to Sterilization) and cleaning validation (AAMI TIR30, A Compendium of Processes, Materials, Test Methods, and Acceptance Criteria for Cleaning Reusable Medical Devices) are the standard references manufacturers use to validate reprocessing instructions (AAMI TIR17:2024; AAMI TIR30:2011). For steam sterilization programs specifically, ANSI/AAMI ST79 is the comprehensive consensus standard covering cycle parameters, biological indicators, and load monitoring (ANSI/AAMI ST79:2017/(R)2022).

Chemical Compatibility Checklist

• Always consult the specific device's manufacturer IFU before selecting a disinfectant or sterilant — generic guidance is not a substitute
• Confirm the disinfectant is FDA-cleared (for HLD/sterilants) or EPA-registered (for LLD/intermediate use) for the intended purpose
• Verify immersion limits — some devices (e.g., ultrasound probes) may only tolerate partial submersion
• Respect exact contact times and dilution ratios; under-dosing risks inadequate microbial kill, over-exposure risks material damage
• Rinse thoroughly with potable water after chemical HLD unless the manufacturer specifies otherwise
• Inspect devices regularly for signs of material degradation (discoloration, cracking, delamination) that may result from repeated chemical exposure
• Never substitute a household or industrial disinfectant for a validated medical-grade product

Why This Matters for Imported Used Equipment

Equipment arriving from a donor hospital or refurbisher has typically already been reprocessed once before shipment. However, biomedical engineers receiving the equipment should not assume that the correct Spaulding-appropriate method was used or that the device's materials remain fully compatible with all disinfectants after years of service. Before returning any critical or semicritical device to clinical use, receiving facilities should independently verify the applicable Spaulding category, re-clean and reprocess according to that category, and confirm chemical compatibility against the current manufacturer IFU — which may differ from older documentation shipped with the unit.