We Should Stop Injecting Unfiltered Room Air into Medication Containers

During more than three decades as a nurse, I have prepared and administered more injectable medications than I could count.

I was taught the same basic technique used throughout healthcare: draw room air into a syringe, inject it into a vial to equalize the pressure, and then withdraw the medication.

Mechanically, it works. As liquid leaves a vial, something must replace that volume. Without replacement air, negative pressure develops and makes continued withdrawal increasingly difficult.

But there is a contradiction in this familiar practice that healthcare has largely overlooked.

We disinfect the stopper. We use sterile needles and syringes. We avoid touching critical surfaces. We carefully control how injectable medications are manufactured, stored, prepared, and administered.

Then we draw unfiltered air from the room and intentionally inject it into the medication container.

I no longer believe that should be considered an acceptable default.

A Sterile Syringe Does Not Make Room Air Sterile

Ambient air is not empty, and it is not sterile.

It contains dust, particles, droplets, bacteria, fungal spores, and other biological material. Its composition changes with ventilation, occupancy, movement, cleaning, human or animal activity, and the surrounding environment.

One study examining the air in 18 hospital wards identified airborne bacterial genera including Staphylococcus, Micrococcus, Corynebacterium, Bacillus, Streptococcus, and Enterococcus.

Not every airborne organism is harmful. But that is not the point.

The point is that room air is variable and uncontrolled. Drawing it into a sterile syringe does not sterilize it. If particles or microorganisms are suspended in that air, the syringe does not somehow make them disappear.

Read the hospital-air study

When we intentionally inject room air into a medication container, we create a direct pathway from the surrounding environment into a system containing an injectable product.

We would not knowingly leave another input into an injectable medication uncontrolled. Air should not receive a special exemption simply because we cannot see what it carries.

This Is More Than a Theoretical Pathway

A 2024 study evaluated a medication-transfer system that required environmental air to be drawn into a syringe and introduced into a vial for pressure equalization.

The researchers tested the system in a sealed environment containing aerosolized human coronavirus OC43. After the environmental air was introduced and liquid was transferred, viral material was detected in the samples.

This was an intentional contamination-challenge study, not an ordinary clinical environment. Detection of viral RNA also does not prove that viable, infectious virus was transferred. The study does not tell us how often routine air injection contaminates a medication or whether it causes infections.

But it demonstrated that the pathway is real: material present in the environment can travel into a medication-transfer system with air introduced for pressure equalization.

Read the environmental-air study

We should not have to prove that every injection of room air causes contamination before recognizing an obvious weakness in the process.

Infection prevention is built on controlling avoidable pathways. We do not normally wait until every possible source of contamination has been connected to a documented patient infection before deciding that a barrier is appropriate.

Unfiltered ambient air is an uncontrolled input. That alone is a legitimate reason to replace it with a more controlled approach.

Familiar Does Not Mean Acceptable

Injecting room air into medication containers is familiar, inexpensive, and effective at solving a pressure problem. Most clinicians have done it without observing an obvious adverse outcome.

But familiarity is not evidence that a practice is optimal.

Healthcare has changed many long-standing practices after someone stopped accepting “that is how we have always done it” as a sufficient explanation. Sometimes the problem was obvious. Other times, it was hidden inside a routine process that had gone unquestioned for years.

Replacement air may be one of those practices.

Rigid medication containers require pressure equalization. That physical requirement is unavoidable.

Using unfiltered room air is not.

Filtered venting is already used in pharmaceutical processing, fluid-storage systems, infusion equipment, and medication-access devices. B. Braun, for example, markets a dispensing pin containing a 0.45 μm bacteria-retentive air filter intended to reduce contamination of medication by environmental air.

That is not proof that every injection of unfiltered air causes contamination. It does demonstrate that filtering environmental air before it enters a medication container is already an established medical-device principle.

View the B. Braun Mini-Spike 2 Filter

If replacement air is worth filtering in one medication-access system, we should be asking why it remains unfiltered in another.

One of the Reasons I Developed I2F

Concern about unfiltered replacement air was one of several reasons I developed I2F.

During my nursing career, I repeatedly saw problems associated with removing medication from rigid bottles: pressure imbalances, interrupted flow, bubbles, foaming, medication left behind, and the need for clinicians to use workarounds simply to keep the medication moving.

I began to question the entire replacement-air process—not only how air affected pressure and fluid movement, but where that air came from and what it might carry into the bottle.

Conventional practice often requires room air to be drawn into a syringe and injected beneath the medication’s surface. I2F takes a more deliberate approach by routing replacement air through a high-efficiency hydrophobic PTFE membrane and delivering it directly to the bottle headspace.

The Porex membrane selected for the new I2F design is rated at 99.99% filtration efficiency at 0.1 μm under the IEST-RP-CC007.2 particulate-filtration test method.

The point is not that filtration makes ambient air perfect. The point is that the air no longer enters untouched.

I2F places a defined, high-efficiency filtration barrier where conventional air injection provides none. Filtered air and unfiltered room air are not equivalent. They are not the same pathway.

One pathway places a filtration barrier between the surrounding environment and the medication container. The other relies directly on whatever happens to be present in the room.

I2F was developed to address several connected problems in medication preparation and delivery. Controlling how necessary replacement air enters the bottle is an important part of that larger purpose.

Replacement Air Is Part of the Medication-Delivery System

Healthcare has treated replacement air as an afterthought for too long.

If air enters a medication container, it becomes part of the medication-handling pathway. Its source, movement, filtration, and point of entry should be considered alongside the needle, syringe, stopper, container, and medication itself.

This issue becomes even harder to ignore when medications are prepared outside highly controlled environments, when larger volumes of air are introduced, when multiple bottles are required, or when the patient receiving the medication is particularly vulnerable.

That is the change I believe healthcare should make: recognize replacement air as part of the medication-delivery system, control the pathway through which it enters, and stop assuming that what we cannot see does not matter.

We should be willing to challenge a familiar practice when a more deliberate approach is available. That is how healthcare improves—not by defending the way something has always been done, but by asking whether we can do it better.

It Is Time to Change the Default

For decades, healthcare has accepted the injection of room air because it solves a pressure problem.

But solving one problem does not justify ignoring another.

We know ambient air is not sterile. We know it carries particles and microorganisms. We have evidence that environmental material can travel with introduced air. We also know how to filter air before it enters a medication container.

Continuing to treat unfiltered room air as the default is no longer good enough.

I believe replacement air should be filtered, controlled, and treated as part of the medication-delivery system. I developed I2F to address several connected problems in medication preparation and delivery—and the uncontrolled introduction of room air was one of them.

Rigid medication containers require replacement air. That physical requirement is unavoidable.

Using unfiltered room air is not.

We would not knowingly leave another input into an injectable medication uncontrolled. We should stop making an exception for air.

References

1. Ling S, Hui L. Evaluation of the complexity of indoor air in hospital wards based on PM2.5, real-time PCR, adenosine triphosphate bioluminescence assay, microbial culture and mass spectrometry. BMC Infectious Diseases. 2019;19:646. https://doi.org/10.1186/s12879-019-4249-z

2. Amichay M, Slutsky Smith EA, Salomon S. Assessment of environmental viral contamination of liquids prepared in a closed system drug transfer device. Pharmacy Practice. 2024;22(4):3091. https://doi.org/10.18549/PharmPract.2024.4.3091

3. Institute of Environmental Sciences and Technology. IEST-RP-CC007.2: Testing ULPA Filters. 2009. View the recommended-practice information

4. Porex. Porex Virtek PTFE Hydrophobic Venting Membrane: PMV20. View the Porex PMV20 information

5. B. Braun. Mini-Spike 2 Filter: Vented dispensing pin with bacteria-retentive air filter. View the product information

Disclosure: Damea Alexander is a nurse, inventor, founder and CEO of Alexander International Innovations, and the inventor of I2F. I2F has not been cleared for human use in the United States. Statements about filtered replacement air describe the device’s design and component specifications. Device-specific microbial and clinical performance require further testing.