How Must an Autoclave Be Loaded? Practical Loading Rules

The correct loading rule set (use this every cycle)

• Do not overload. Leave visible gaps so steam can circulate around each item; if items touch tightly, air pockets form and sterilization can fail.
• Keep all items off the chamber floor by using the manufacturer’s rack/tray; do not place packs directly on the metal base.
• Do not allow packages to touch chamber walls or the door (condensation and cold spots increase wet packs and drying failures).
• Load by “gravity”: rigid/heavy items on the bottom, wrapped/light items above to reduce dripping and compression.
• Keep hinged instruments open and disassembled sets arranged so joints and lumens are not blocked.
• Use racks for pouches and keep them edge-on whenever possible; flat stacking is a common cause of wet packs.

Practical check: if you cannot slide two fingers between most packages, the load is likely too dense and should be split.

Why loading matters (steam can’t sterilize what it can’t reach)

Steam sterilization depends on saturated steam contacting surfaces long enough to transfer heat and condense. Poor loading creates three predictable failures: trapped air, shadowed surfaces, and retained condensate.

A realistic failure example

If ten peel pouches are stacked flat into a tight pile, the middle pouches can stay cooler and wetter. Even if the cycle completes, the center may dry slowly and can emerge with damp paper, which compromises the sterile barrier. Splitting into two loads or using an edge-on rack typically resolves this.

Bottom line: the “right” load is one that matches the cycle’s validated performance and allows free steam circulation and effective drying.

Prepare items before they go into the chamber

Instruments and sets

• Open hinged instruments and unlock ratchets so steam reaches joints and serrations.
• Disassemble multi-part devices; do not nest parts so tightly that surfaces are shielded.
• Keep lumens oriented to drain (avoid “cups” that trap water). If lumen devices require special adapters or cycles, use them only as specified by the device IFU.

Wrapped packs, cassettes, and peel pouches

• Do not overstuff packaging; bulging packs restrict air removal and drying.
• Place an internal chemical indicator in each package and label externally per your process controls.

Liquids and waste (only if your autoclave and policy permit)

Liquids and waste require different containment and venting than instrument loads. A practical example is filling a 1 L bottle to 600–700 mL to leave headspace, loosening caps, and using a secondary tray to catch boil-over. Never mix liquid loads with dry packs in the same cycle unless your validated cycle specifically allows it.

Load layout rules inside the chamber

If your sterilizer uses a gravity cycle, correct orientation and spacing become even more important because air removal is less aggressive than in pre-vacuum cycles.

Practical loading patterns by item type

Peel pouches

1. Use a pouch rack; load pouches on edge rather than flat.
2. Alternate faces (paper-to-plastic, pouch-to-pouch) to reduce sticking and improve drying.
3. Keep seals unobstructed; do not clamp pouches under heavy items.

Wrapped packs and instrument trays

• Place packs flat and avoid stacking packs directly on top of each other.
• Separate trays so condensate can drain; do not create “roofs” that drip onto paper packaging.
• If mixing rigid items and soft wraps, place rigid/heavy items below and leave extra drying time if your cycle supports it.

Rigid containers

• Keep vents/filters unobstructed and load containers level to maintain designed airflow paths.
• Do not overpack containers; use the manufacturer’s weight and configuration limits.

Liquids (if applicable)

• Use secondary containment and space bottles apart to prevent uneven heating.
• Ensure headspace (example: fill to 60–70%) and vent caps as required by policy to reduce burst risk.

Common loading mistakes and immediate fixes

• Mistake: Packs touching chamber walls. Fix: Reposition on the rack and reduce load width so nothing contacts the vessel.
• Mistake: Flat-stacked pouches. Fix: Use an edge-on pouch rack and split into two runs if needed.
• Mistake: Heavy metal above paper packaging. Fix: Put rigid/heavy items on the bottom shelf to reduce dripping and crushing.
• Mistake: “Tight puzzle” packing. Fix: Create intentional air gaps; when in doubt, run a smaller load.

If you are repeatedly seeing wet packs, the fastest operational improvement is usually lower load density plus correct pouch racking and adequate drying time.

How to verify the load was acceptable

Indicators and placement

Verification complements correct loading. Place internal chemical indicators inside each pack and use external indicators as required. For routine monitoring, run a biological indicator per your policy and place it in the most challenging part of the load (commonly the densest area or the area historically slow to dry/heat).

A simple documentation example

• Load ID: date/time + operator initials (e.g., 2026-01-18 AM / JD)
• Cycle type: gravity or pre-vac (as configured)
• Load description: “12 pouch rack items + 2 wrapped trays, bottom shelf reserved for trays”
• Results: external/internal indicator pass, BI result (if used), notes on wet packs or rework

Conclusion: the safest way to load an autoclave

How must an autoclave be loaded? Load it loosely and deliberately: keep items on racks, prevent contact with walls, avoid stacking, orient pouches edge-on, put heavy items below lighter packaging, and run only validated load configurations for the chosen cycle.