What Is a Chemical Sterilizer and How Does It Work?

A chemical sterilizer uses reactive liquids or gases to destroy or inhibit microbes on medical devices and instruments, especially those sensitive to heat. What is sterilization? It is a process that eliminates all forms of microbial life, which plays a vital role in healthcare for infection control and patient safety. Chemical sterilizer, often called germicides, works at low temperatures and provide an option for items that cannot withstand high heat. Unlike physical methods, chemical sterilization relies on direct contact with the material, requiring careful handling to prevent exposure or residue.

The table below shows key differences between physical and chemical sterilization methods:

Key Takeaways

• Chemical sterilizer uses special liquids or gases to kill all microbes on heat-sensitive medical tools without using high heat.
• The works by breaking down vital parts of germs, stopping them from living or growing, making them safe for delicate instruments.
• There are two main types: liquid sterilizers for soaking items and gas sterilizers like ethylene oxide for deep, thorough sterilization.
• Chemical sterilizer is essential for cleaning plastic, rubber, and electronic devices that steam or heat can damage.
• Proper handling, safety gear, and monitoring ensure chemical sterilization works well and keeps both users and patients safe.

Chemical Sterilizer Basics

What Is It?

A chemical sterilizer is a device or system that uses specific chemicals in liquid or gaseous form to eliminate all forms of microbial life, including bacteria, viruses, fungi, and spores, from medical instruments and laboratory equipment. This process answers the question, what is sterilization, by providing a method that does not rely on high temperatures. Chemical sterilizer plays a crucial role when heat-sensitive materials, such as certain plastics, rubbers, or delicate electronics, require thorough decontamination.

The most widely used chemical sterilizers in medical and laboratory settings include:

• Ethylene oxide combined with carbon dioxide (gaseous sterilizer)
• Ozone gas for oxidizing organic matter
• Hydrogen peroxide, nitrogen dioxide, and formaldehyde solutions (liquid sterilizers)
• Glutaraldehyde and peracetic acid for high-level disinfection
• Ethanol at 70% concentration for laboratory equipment
• Disinfectants like quatricide and super oxidized water for specific cleaning tasks

These chemicals work by denaturing proteins and disrupting cell structures, which leads to the destruction of microorganisms. Chemical sterilizer is preferred when heat sterilization is unsuitable due to the sensitivity of the items being treated.

Note: Gaseous sterilizers, such as ethylene oxide, penetrate materials quickly and provide effective sterilization without damaging delicate items.

The table below summarizes the primary chemical components found in commercial chemical sterilizers and their key characteristics:

Main Function

The main function of a chemical sterilizer is to ensure that all microorganisms, including the most resistant spores, are destroyed on instruments and surfaces. In infection control protocols, chemical sterilizer provides immediate visual confirmation that sterilization conditions have been met. Many systems use heat-sensitive chemicals that change color when exposed to specific parameters, such as temperature, time, or the presence of steam. This color change acts as a process indicator, showing that the sterilizing agent has penetrated the packaging and reached the instruments inside.

Chemical sterilization supports patient safety by preventing the use of non-sterilized instruments. It also ensures that healthcare providers follow proper sterilization procedures. Chemical monitoring, which includes these visual indicators, complements biological monitoring and helps confirm the effectiveness of the sterilization process.

Tip: Chemical sterilizer offers rapid sterilization without heat, making it ideal for items that cannot withstand high temperatures. However, users must handle these chemicals with care, as many are hazardous to humans but do not damage the items being sterilized.

How Chemical Sterilizer Works?

Mechanisms

Chemical sterilizer destroys microorganisms through specific chemical reactions. Ethylene oxide acts as a direct alkylating agent. It reacts with proteins and nucleic acids inside bacteria and viruses. This reaction substitutes hydrogen atoms on vital molecules, disrupting their functions and stopping microbial growth. Moisture, temperature, and ethylene oxide concentration enhance this process. Plasma sterilization uses super-oxidizers such as hydrogen peroxide. These oxidizers attack and break down essential life-supporting molecules. Oxidation damages cell walls and genetic material, leading to cell death.

Both alkylation and oxidation are powerful methods of sterilization. Alkylation targets DNA and proteins, while oxidation destroys cell membranes and other critical structures. These reactions do not require high temperatures, making chemical sterilizers ideal for heat-sensitive items. However, strong oxidizers can damage delicate materials, so users must select the right sterilization process for each application.

Chemical sterilizer works by disrupting the building blocks of life in microorganisms. This ensures that bacteria, viruses, and spores cannot survive or reproduce.

Process Steps

The sterilization process with chemical sterilizer follows a series of steps to ensure safety and effectiveness. Each step plays a role in achieving complete sterilization and maintaining the integrity of medical devices.

1. Receiving, Cleaning, and Decontamination
   Staff collect reusable instruments and remove all visible debris. Cleaning uses detergents and water or automated chemical cleaning systems. Rinsing removes any chemical residues.
2. Preparation and Packaging
   Workers inspect, dry, and assemble instruments. Packaging maintains sterility and allows chemical agents to reach all surfaces.
3. Sterilization
   Operators load instruments into FDA-cleared sterilizers. For chemical sterilization, they use unsaturated chemical vapor sterilizers or gas sterilizers. The process applies chemicals such as ethylene oxide, hydrogen peroxide, or formaldehyde at controlled temperature and pressure. Exposure time varies based on the chemical and device type.
4. Monitoring and Sterility Assurance
   Staff document mechanical, chemical, and biological monitoring results for each cycle. Chemical indicators confirm that sterilization conditions have been met. Biological indicators verify the destruction of highly resistant spores.
5. Storage
   Sterile items are stored in covered, dry areas away from contamination risks. Staff maintain records and periodically revalidate the sterilization process to comply with regulatory standards.

The effectiveness of chemical sterilization depends on several factors. The table below summarizes the most important ones:

Staff must monitor chemical concentration, exposure time, and temperature during every sterilization process. These factors ensure that the chosen methods of sterilization achieve the desired level of safety.

Types of Chemical Sterilizer

Chemical sterilization methods fall into two main categories: liquid sterilizers and gas sterilizers. Each type uses different chemicals and suits specific applications, especially for items that cannot tolerate steam sterilization.

Liquid Sterilizers

Liquid sterilizers use powerful chemicals to kill or inactivate microbes on medical devices. The most common liquid sterilant is peracetic acid, often used at a 35% concentration in automated systems. Peracetic acid works by denaturing proteins and disrupting cell walls, making it effective against a wide range of microorganisms. Healthcare workers often use liquid sterilizers for heat-sensitive, immersible devices such as endoscopes and bronchoscopes. The process requires precise control of concentration, exposure time, and temperature.

Other chemicals like glutaraldehyde and ortho-phthalaldehyde (OPA) also serve as high-level disinfectants. Glutaraldehyde offers excellent compatibility with many materials but can cause respiratory irritation and works slowly against spores. OPA provides good material compatibility and does not fix tissues, but it may stain proteins and has limited clinical experience. Hydrogen peroxide and phenolics are sometimes used, but they may damage metals like brass and copper.

Note: Liquid chemical sterilization is ideal for semi-critical devices that cannot withstand steam sterilization, but it does not provide the same sterility assurance as gas or steam methods.

Gas Sterilizers

Gas sterilizers use chemicals in vapor or gas form to achieve sterilization. Ethylene oxide sterilization stands as the most widely used method for heat-sensitive devices. Ethylene oxide penetrates complex device structures and achieves a high sterility assurance level, even inside narrow lumens. Hospitals and manufacturers rely on ethylene oxide sterilization for items that cannot tolerate high temperatures or moisture.

Other gas sterilizers include hydrogen peroxide gas plasma, vaporized hydrogen peroxide, ozone, and formaldehyde. Hydrogen peroxide gas plasma sterilizers use advanced technology to sterilize delicate instruments quickly. Ozone and chlorine dioxide offer eco-friendly options, especially in food processing and decontamination. Each gas sterilizer has unique compatibility and safety considerations, so users must match the method to the device material and clinical need.

Gas sterilizers provide higher sterility assurance than liquid methods. Ethylene oxide sterilization remains the gold standard for many heat-sensitive medical devices, offering reliable results where steam sterilization is not possible.

When to Use?

Heat-Sensitive Items

Chemical sterilizer plays a vital role when sterilizing items that cannot withstand high temperatures or moisture. Many medical devices, such as flexible endoscopes, scissors, stethoscopes, oral and rectal thermometers, and laser probes, contain materials like plastics, silicone, or embedded electronics. These materials degrade or lose function if exposed to steam or dry heat. Chemical sterilization methods, including ethylene oxide gas and hydrogen peroxide gas plasma, offer a safe alternative for these devices.

• Chemical sterilizer is preferred for:
  • Devices made of plastic, rubber, or fiber optics
  • Surgical instruments with delicate components
  • Items that rust or corrode in moist or high-temperature environments
  • Equipment with complex shapes or narrow lumens

Chemical sterilizer allows healthcare professionals to maintain the integrity of heat-sensitive surgical instruments while ensuring complete sterility.

Steam sterilization remains unsuitable for many polymers and materials sensitive to heat or moisture. Chemical methods, such as peracetic acid or glutaraldehyde, provide effective sterilization without damaging these items.

Healthcare Settings

Hospitals, dental clinics, and outpatient centers rely on chemical sterilizer for a wide range of applications. These facilities use chemical sterilization for surgical instruments and other tools that cannot tolerate high temperatures. Dental impressions, delicate dental instruments, and equipment with intricate surfaces often require chemical sterilization.

Common chemical sterilizers in healthcare include glutaraldehyde, hydrogen peroxide, unsaturated chemical vapor, and peracetic acid. Glutaraldehyde disinfects dental impressions and equipment, while hydrogen peroxide vapor penetrates complex surfaces and leaves no toxic residue. Unsaturated chemical vapor sterilization reduces corrosion on steel surgical instruments, making it suitable for dental burs and other metal tools.

• Key uses in healthcare settings:
  • High-level disinfection of semicritical and critical items
  • Sterilization of surgical instruments that contact mucous membranes or sterile tissues
  • Maintaining sterility for items incompatible with heat-based methods

Proper cleaning, control of exposure time, and correct chemical concentration are essential for effective sterilization and patient safety.

Effectiveness and Safety

Efficacy

Chemical sterilizer provides a high level of microbial kill, making them essential for effective sterilization techniques. The machine eliminates bacteria, viruses, fungi, and spores, even on heat-sensitive items. Studies show that commercial liquid sterilants, such as glutaraldehyde and peroxi compounds, can reduce bacterial spores by 2,500-fold to 56,000-fold after 10–11 hours. However, the ideal standard for sterilization is a 6-log reduction, which equals a 99.9999% decrease in microbial populations. Some sterilants, including ethylene oxide, peracetic acid, hydrogen peroxide gas plasma, and chlorine dioxide, achieve this level of reduction within seconds for certain bacteria.

Chemical sterilization matches the microbial kill rates of steam sterilization and dry heat, but it often requires longer exposure times. Steam sterilization works faster but cannot be used for heat-sensitive materials. Chemical methods remain vital for items that cannot tolerate high temperatures.

Safety Tips

Operators must follow strict safety protocols when using chemical sterilizer. Regulatory agencies like the FDA and EPA require adherence to product labeling and instructions. Key safety tips include:

• Wear personal protective equipment (PPE) such as lab coats, gloves, and face shields.
• Receive proper training before operating sterilization equipment.
• Inspect all items for damage before sterilization.
• Use only compatible packaging materials.
• Monitor each sterilization cycle with chemical and biological indicators.
• Store sterile items in clean, dry, and well-ventilated areas.
• Report equipment malfunctions immediately.

Always follow manufacturer’s instructions and never use chemical sterilizer for flammable or reactive materials. Proper handling ensures both user safety and effective sterilization.

Risks

Chemical sterilizer, while effective, poses health and environmental risks. Ethylene oxide can cause respiratory irritation, headaches, and nausea after short-term exposure. Long-term exposure increases the risk of cancer, reproductive issues, and genetic changes. Glutaraldehyde may irritate the skin, eyes, and respiratory tract, and chronic exposure can lead to asthma or other health problems.

• Acute risks: respiratory irritation, headaches, nausea, dermatitis.
• Chronic risks: cancer, reproductive effects, asthma, genetic changes.

Environmental risks also exist. Improper disposal of chemical residues can contaminate soil, water, and air. Incineration of medical waste with chemical residues may release toxic pollutants like dioxins and heavy metals. Proper waste segregation and disposal help reduce these risks.

Facilities should use modern incinerators and follow strict waste management protocols to protect both people and the environment.

Conclusion

A chemical sterilizer provides essential sterilization for heat-sensitive instruments in healthcare and industry. Selecting the right method depends on device material, workflow, and safety needs. Recent advancements, such as hydrogen peroxide vapor and cold plasma, improve efficiency and sustainability. Facilities should follow best practices for safe use:

• Train staff regularly and use personal protective equipment.
• Preclean instruments and monitor cycles with chemical indicators.
• Maintain documentation and comply with regulatory guidelines.

FAQ

What Items Should Not Be Sterilized with Chemical Sterilizer?

Items made from cellulose, such as paper or cotton, should not go into chemical sterilizer. These materials can absorb chemicals and may not become fully sterile. Electronics with sensitive components may also get damaged by certain chemicals.

How Long Does Chemical Sterilization Take?

The process time varies by chemical type and device. Ethylene oxide sterilization can take several hours, including aeration. Liquid sterilizers like peracetic acid may require 30 to 60 minutes. Always check the manufacturer’s instructions for exact times.

Is Chemical Sterilizer Safe for the Environment?

Chemical sterilizer can harm the environment if not handled properly. Facilities must follow strict disposal guidelines. Some newer sterilizers, such as hydrogen peroxide vapor systems, produce fewer toxic byproducts and offer safer alternatives.

Can Chemical Sterilization Replace Steam Sterilization?

Chemical sterilization works best for heat-sensitive items. Steam sterilization remains the gold standard for most metal instruments. Facilities often use both methods to cover different needs.

What Precautions Should Staff Take When Using Chemical Sterilizer?

Staff should wear gloves, masks, and eye protection. Proper ventilation is important. Training helps prevent accidents. Always follow safety data sheets and manufacturer guidelines.