What Materials Are Autoclavable? What are the Different Types of Autoclaves?

Different Types of Autoclavable Materials

Autoclaves are used to sterilize materials for use or reuse in various industries, namely industrial, healthcare, and scientific research. They are high-tech machines that sterilize with pressurized steam. Steam sterilization is a preferred choice because it’s non-toxic and inexpensive.

Determining what materials are suited for the autoclave process is important. Incompatible materials cannot stand the pressure and heat of this sterilization method. Additionally, improper loading of these materials into an autoclave can result in property damage and concerns over health and safety. Anyone working with an autoclave should understand what types of materials are autoclavable so that accidents can be avoided.

What Materials Are Autoclavable?

Autoclavable materials can withstand the heat and pressure without damage or exploding. These materials are safe to use within an autoclave as long as all safety guidelines are followed:

1. Glass

Glass is generally considered a safe material for autoclaving. Borosilicate glassware (Pyrex) is usually preferred because of its low-thermal-expansion properties, although referring to the manufacturer’s information before autoclaving any glass instrument or container is best.

Avoid autoclaving any glass material with a lid. Only fill the glass container ⅔ full and remove the lid to prevent the material from exploding.

2. Polycarbonate Plastics

Polycarbonate plastic is used for bottles, desiccators, vacuum chambers, and other tools where visibility is important. Polycarbonate materials can be safely autoclaved, but only for a certain number of cycles. With each additional autoclave cycle, the strength of the material is lowered. Polycarbonate plastics can be autoclaved for 30-50 cycles.

3. Polypropylene & Polypropylene Copolymer

Polypropylene is a plastic resin popular for its durability and low cost. Polypropylene is used to manufacture all kinds of plastic pans, trays, and even bags. Polypropylene and polypropylene copolymer products can be repeatedly autoclaved without losing strength. Certain polypropylene wipes, as well as select polyester wipes can be autoclaved. It’s important to check with the manufacturer for exact recommendations on specific products.

4. Metals

Most metal materials used in laboratory settings are autoclavable and highly resistant to corrosion. The same applies to healthcare settings, where stainless steel surgical instruments can be autoclaved without issue.

5. Pipette Tips

Pipette tips are an important component of laboratory research. But some pipette tips are polyethylene (which will melt when autoclaved), so all pipette tips should be autoclaved within a biohazard bag.

6. Paper

Paper can be autoclaved, but it will combust if not placed inside a compatible waste bag and autoclaved on the steam setting.

7. Latex or Vinyl Gloves

Latex or vinyl gloves must be autoclaved inside a biohazardous autoclavable waste bag before being sterilized. They will melt slightly but won’t burn when placed properly in a waste bag.

8. Hospital Linens & Other Textiles

Hospitals can safely autoclave their linens and textiles from patient gowns, bedding, and other sources.

9. Culture Plates

Petri dishes and agar plates can be autoclaved if proper procedures are followed.

What Materials Are Not Autoclavable?

To protect the health and safety of operators, ensure materials aren’t damaged and avoid damaging the autoclave and voiding the warranty, only compatible materials should be autoclaved. Any material that has contacted volatile or corrosive chemicals, even normally compatible materials, should not be autoclaved. Radioactive materials and anything containing mutagens, teratogens, or carcinogens should never be loaded in an autoclave.

In addition to those guidelines, here’s a short list of materials that are not autoclavable:

  • Liquid in sealed contains
  • Pharmaceuticals
  • Explosive & flammable materials
  • Acids and organic solvents
  • Chlorine, Bleach, or hypochlorite
  • Non-stainless steel
  • Seawater
  • Anything contaminated by radiation
  • The following plastic materials:
    • Polystyrene (Styrofoam)
    • Polyurethane (synthetic resin used for furniture staining)
    • Low-density polyethylene (squeeze bottles, plastic bags, saran wrap)
    • High-density polyethylene (shampoo bottles, bleach bottles, cutting boards)

What are the Different Types of Autoclaves?

There are two common types of autoclaves for steam sterilization: highspeed pre-vacuum autoclaves and gravity displacement autoclaves. Both types can be purchased in various sizes with different configurations and features. And both sterilize through high-temperature steam and pressure, but they operate through two different mechanisms:

Highspeed Pre-Vacuum Autoclave

Highspeed pre-vacuum autoclaves use a vacuum to remove all ambient air from the sterilizing chamber before steam is pumped in. This method is best for materials that are porous or large. It can be used for any material where removing the ambient air is difficult. When the steam is added to the chamber, it can sterilize areas that normally contain ambient air.

Gravity Displacement Autoclave

With a gravity displacement autoclave, steam is injected through the top and size of the autoclave into the sterilizing chamber. Steam is heavier than air, so it forces the air within the chamber to exit the chamber through the bottom drain vent. By forcing the ambient air from the chamber, the steam can fully sterilize the materials.

Gravity displacement autoclaves are well-suited for sterilizing common laboratory media. This type of autoclave is simple to operate, effective, and affordable. Because of this, they are the most widely used and commonly recommended autoclaves on the market.

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