Storage of Medical Supplies: How Can the Sterility Period Be Extended?

The Final Stage of Sterilisation: Storage and Logistical Safety

In healthcare facilities, the sterilisation cycle does not end when the autoclave door is opened or the sterilisation device completes its cycle. Ensuring that a perfectly sterilised medical device retains its sterility until it reaches the operating theatre or the patient depends entirely on the proper management of the storage and logistics stages. The reliability of a sterile package at the moment it is opened in the operating theatre is directly related not only to the sterilisation equipment but also to the physical conditions of the storage facility where the materials are kept.

In current infection control guidelines, the storage period for sterile materials is addressed not merely as a fixed duration based on calendar days, but through an ‘event-related sterility’ approach. In other words, the duration for which a material remains sterile depends on dynamic factors such as the physical stress to which the package is subjected, the particle density of the environment, fluctuations in humidity and temperature, and the number of times it is handled. In this guide, we examine medical storage management sterilisation standards and ways to maintain sterility at the highest level for storage managers and logistics units.

I. Climate Control and Physical Environmental Conditions in Sterile Storage Areas

Areas where sterile materials are stored are subject to far stricter environmental criteria than a standard hospital storeroom. Even the slightest deviation in climate control parameters can lead to the breakdown of the packaging barrier and microbiological contamination.

A.    Temperature and Relative Humidity Parameters

• In sterile storage areas, temperature and relative humidity must be maintained within the limits specified by the organisation and in accordance with the recommendations of the product and packaging manufacturers. Avoiding extreme fluctuations in temperature and humidity is crucial for preserving the physical integrity of sterile packaging.
• High Humidity Risk: High levels of relative humidity can cause paper and non-woven wraps to become damp, adversely affecting the physical integrity of the packaging. In particular, if the packaging becomes wet, this can make it difficult to maintain the sterile barrier, thereby increasing the risk of contamination.
• Low Humidity Risk: Very low relative humidity can affect the physical properties of certain packaging materials, increasing the risk of drying out and brittleness. Therefore, storage conditions for sterile packaging must be managed taking into account the properties of the materials used and the manufacturer’s recommendations.

B. Airflow, Positive Pressure and Filtration

Sterile storage areas must be maintained under positive pressure relative to corridors and adjacent rooms. The outflow of clean air whenever a door is opened prevents dust and microorganisms from the external environment from entering the storage area. HEPA filters must be used in the ventilation system, and a minimum of 4 to 10 air changes per hour must be ensured.

II. Shelving Systems and Physical Layout Standards

The structure of the shelving used to store sterile materials must be designed in such a way as not to obstruct air circulation or exert physical stress on the packaging.

A. Critical Distance Rules

In a medical storage facility compliant with international standards, the following physical distance rules must be strictly adhered to:

• Height from the Floor: The lowest shelf must be at least 20 to 25 cm above the floor to protect against water and chemicals that may splash during floor cleaning.
• Distance from the Ceiling and Fire Sprinklers: The top level of sterile materials must be kept at least 45 cm below the sprinkler head so as not to impede the effective operation of the fire sprinklers. This distance is particularly important for storage located directly beneath the sprinklers.
• Distance from External Walls: To prevent the transfer of moisture and heat, shelving must be kept at least 5 cm away from external walls.

B. Selection of Shelving Materials: Distinction Between Wire Shelving and Solid Shelving

In sterile storage areas, wire shelving systems made of stainless steel or with an epoxy coating, which prevent dust accumulation, should be preferred. However, a solid protective base plate must be placed beneath the lowest wire shelf to prevent vapours from mops and cleaning solutions used during floor cleaning from reaching the packages.

III. Packaging and Sterility: Maintaining Barrier Integrity

Packaging is the sole defence ensuring that a medical device remains sterile. Unless the correct balance between packaging and sterility is established, even the most advanced storage facility cannot prevent contamination.

A. Risk Management by Packaging Type

• Rigid Sterilisation Containers: These provide the highest level of protection against physical impact and pressure. The integrity of the filter seals and locking mechanisms must be checked regularly during storage.
• Non-Woven (SMS) Pouches: These are flexible and vapour-permeable but are sensitive to friction and internal pressure from sharp or piercing instruments. Heavy sets must not be removed from the shelf by pulling on a single point in this type of packaging.
• Paper/Plastic Sterilisation Bags: The transparent film surfaces of the bags are susceptible to tearing and creasing. Bags must never be folded, bent or secured together with rubber bands.

B. Handling Rules

The more times a sterile pack changes hands before reaching the operating theatre, the greater the risk of contamination.

1. Cooling Time: Hot packs emerging from the autoclave must not be transferred to storage until they have cooled completely to room temperature. When a hot pack comes into contact with a cold shelf, condensation forms inside.
2. Storage Without Compression: When placing materials on shelves, packages must not be compressed, and excessive stacking must be avoided.
3. Lifting Technique: Packages should be lifted by supporting them from underneath with both hands, rather than being dragged.

IV. Medical Warehouse Management: Logistics and Stock Rotation in Sterilisation Processes

Proper planning of stock flow ensures that packages are used before their shelf life expires or they suffer physical damage.

A. The FIFO and FEFO Principles

In storage processes, the FIFO (First In, First Out) principle, or the FEFO (First Expired, First Out) rule for products with expiry dates, must be strictly applied. Newly arrived sterile sets should be placed at the back of the shelves, whilst those due for use should be arranged at the front.

B. Closed Transfer Systems and Internal Logistics

During the transfer of sterile supplies from the central storeroom to operating theatres, intensive care units or outpatient clinics, fully enclosed transfer trolleys must be used instead of open baskets. These trolleys prevent particles caused by air turbulence and foot traffic in hospital corridors from settling on the surface of the packages.

V. Warehouse Hygiene and Disinfection Protocols: The Detro Healthcare Approach

The cleaning of medical storage areas requires different chemical and mechanical protocols to those used for standard room cleaning.

• Dust-Free Surface Disinfection: Warehouse floors and shelf surfaces must never be cleaned by dry sweeping. Wet wiping must be carried out using dust-free, residue-free, broad-spectrum floor and surface disinfectants.
• Quick-Drying Surface Cleaners: Products used for shelf cleaning must dry quickly and must not transfer chemical vapours to the materials.
• Staff Hand Hygiene: Warehouse managers must ensure hand hygiene using alcohol-based hand sanitisers before handling sterile materials.

Zero Risk of Contamination with Flawless Storage

No matter how successful the sterilisation of medical devices may be, unsuitable storage conditions can render the entire process ineffective. Warehouse climate control, correct shelf spacing, the preservation of packaging integrity and trained logistics staff are the key elements that prevent the chain of sterility from being broken. At Detro Healthcare, we support you in achieving the highest microbiological safety standards in your hospital logistics processes through our surface disinfection, hand hygiene and environmental sanitation solutions.

Frequently Asked Questions

1. How is the storage period for sterile materials determined?

According to current standards, the storage period for sterile materials is determined not solely by calendar days, but according to the event-based sterility principle. As long as the packaging remains intact, undamaged, dry and stored under suitable climatic conditions (temperature, humidity), the material is considered sterile.

2. Why must sterile packs be kept at least 20 cm above the floor?

This distance is essential to prevent splashes from water and disinfectants used during floor cleaning, and to prevent dust particles carried by air currents at floor level from coming into contact with the packaging.

3. Does folding or stapling sterilisation pouches compromise sterility?

It certainly does. Folding the bags causes microscopic cracks in the paper and plastic layers. Using a stapler or paperclip, on the other hand, pierces the packaging, completely destroying the sterile barrier.

4. Why should hot packages coming out of the autoclave not be placed in storage immediately?

When hot packages are placed directly onto cold storage shelves, condensation forms inside the packaging due to the temperature difference. As wet packages will attract bacteria from the external environment, they are considered contaminated.

5. Why is positive pressure required in sterile storage areas?

Positive pressure ensures that air flows from the inside outwards when the door is opened. This prevents dirty and dusty air from the corridor from seeping into the sterile storage area.