Dry Ice in Temperature-Sensitive Transport: A Useful Tool with Hidden Risks

In biotechnology and pharmaceutical logistics, dry ice is widely used to transport temperature-sensitive materials such as biological samples, reagents, or pharmaceutical products.

Because it is so common, it often looks harmless. The small white pellets producing clouds of fog can even appear almost playful.

But dry ice can create a hazard that is not always obvious.

Why Dry Ice Can Be Dangerous

While the extreme cold is easy to understand, dry ice is actually the solid form of carbon dioxide (CO₂). Instead of melting, it sublimates directly into gas.

This transformation is significant: 1 kg of dry ice produces about 540 litres of CO₂ gas.

Considering that normal atmospheric CO₂ concentration is only 0.04%, even small quantities of dry ice can rapidly increase CO₂ levels in enclosed or poorly ventilated spaces.

Because CO₂ is colourless, odourless and heavier than air, it can accumulate unnoticed — especially in low areas or inside containers.

In some situations, the atmosphere inside containers storing dry ice can become almost pure CO₂, meaning oxygen levels may drop to unsafe levels.

Although CO₂ exposure is the primary concern, dry ice presents other hazards as well. Direct contact can cause severe cold burns or frostbite, requiring appropriate gloves. Because sublimation generates large volumes of gas, dry ice should never be stored in sealed containers, as pressure can build up and cause rupture. During transport or storage, CO₂ can also accumulate in vehicles, elevators, or small rooms when ventilation is limited.

The Main Risk: Hypercapnia

Exposure to elevated CO₂ levels can lead to hypercapnia, a condition where the body accumulates excessive carbon dioxide.

Early symptoms may include:

• headache

• dizziness

• shortness of breath

• confusion

At higher concentrations, the effects can escalate quickly and impair a person’s ability to react safely.

A Real Workplace Situation

During routine operations, a worker attempted to retrieve pellets from a large insulated container storing around 130 kg of dry ice. To reach the pellets, he leaned into the container.

Because dry ice continuously sublimates, the atmosphere inside had become heavily enriched with CO₂. By placing his breathing zone inside the container, the worker was exposed to extremely high concentrations.

Within a short time he experienced dizziness, headache, shortness of breath and confusion.

A portable gas monitor was present at the site — but it was plugged in to charge and not actively monitoring. The workers were not aware of this.

CO₂ exposure above recommended limits can also occur with much smaller quantities, especially when ventilation is limited.

CO₂ Concentration Reference Levels

CO₂ Concentration	Reference Level	What It Means
~420 ppm (0.04%)	Normal atmospheric air	Typical outdoor air concentration.
5,000 ppm (0.5%)	Occupational Exposure Limit (8-hour TWA)	Maximum average concentration recommended for an 8-hour workday.
30,000 ppm (3%)	Short-Term Exposure Limit (STEL)	Short exposure may cause noticeable physiological effects such as headache or increased breathing rate.
40,000 ppm (4%)	IDLH – Immediately Dangerous to Life or Health	Exposure can quickly become dangerous and impair the ability to escape safely.

Simple Precautions

A few simple precautions can significantly reduce the risk:

• use CO₂ monitoring where dry ice is handled

• ensure adequate ventilation

• train workers to recognise symptoms and understand the hazard

• avoid leaning into containers or working close to the floor where CO₂ may accumulate

• keep work areas tidy and avoid leaving pellets on the ground

Local ventilation arm capturing CO2 at the source

It is also important to remember that dry ice keeps sublimating even when nobody is around. This can create unexpected conditions when workers enter the area the next morning.

Final Thought

Dry ice may look harmless, but the gas it releases can quietly change the atmosphere around it.

Treat it with the same respect as any other industrial hazard:

understand it, monitor it, and train your team accordingly. ❄️