Carbon Dioxide Tolerance and Toxicity

5 min read · 11 March 2026

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Carbon Dioxide Tolerance and Toxicity by Lambertsen, published in 1971 in IFEM Report No. 2-71, addresses how the body responds to carbon dioxide and when exposure becomes harmful. These questions matter underwater because breathing equipment, exertion and the surrounding pressure can all shape ventilation and gas exchange.

Why does carbon dioxide matter to divers?

Carbon dioxide is produced by the body as it uses oxygen and is carried in the blood to the lungs for removal. Breathing must continually match production with exhalation: if ventilation is inadequate for the body’s needs, carbon dioxide can accumulate.

Underwater, breathing is not simply a matter of choosing to take a deeper breath. Equipment resistance, gas density, workload and breathing pattern can influence how effectively a diver ventilates. Retaining carbon dioxide may add to discomfort and impair judgment or coordination, both of which are important to safe performance.

What do tolerance and toxicity mean?

Tolerance concerns how a person responds to elevated carbon dioxide and how well they can continue functioning. Toxicity refers to harmful effects from exposure. The terms describe related but distinct parts of a physiological question: the body’s response, and the point at which that response becomes dangerous.

Carbon dioxide affects the regulation of breathing and the body’s acid–base balance. Rising levels can stimulate a strong urge to breathe and produce symptoms such as headache, breathlessness, confusion or impaired decision-making. The response varies with exposure conditions and the individual, so a sensation alone cannot reliably measure the degree of physiological disturbance.

Which underwater conditions shape exposure?

Dive physiology considers the interaction between the diver, the breathing gas, the equipment and the environment. A diver working hard produces more carbon dioxide; if ventilation does not keep pace, retention may become more likely. Stress and task demands can also affect breathing patterns and the ability to recognise or respond to warning signs.

Ventilation: How much gas reaches the lungs and how effectively it removes carbon dioxide.
Workload: Muscular effort increases the body’s carbon dioxide production.
Breathing equipment: Resistance and dead space can influence the effort and effectiveness of breathing.
Pressure and gas properties: The underwater environment changes the physical conditions of breathing.
Recognition: Symptoms and performance changes are relevant, but are not a substitute for physiological assessment.

How does this subject fit into diving research?

Carbon dioxide exposure connects respiratory physiology with dive equipment design, operational practice and medical assessment. Work on tolerance and toxicity helps frame questions about how breathing systems perform under demanding conditions, how exposure affects function, and how risks can be recognised and controlled.

The subject also relates to broader concerns in hyperbaric medicine, where pressure and gas exchange are central to understanding human responses. In that wider field, carbon dioxide is considered alongside oxygen delivery, ventilation and the conditions that influence breathing. The 1971 publication sits within this long-running scientific interest in how people breathe and function in underwater and pressurised environments.

What should divers and clinicians take from the topic?

Carbon dioxide retention is a physiological concern, not merely a matter of comfort. Underwater, impaired thinking or physical performance can have consequences beyond the diver’s immediate symptoms, while equipment and workload may complicate the picture.

This subject is useful for divers, scientific teams, diving physicians and hyperbaric clinicians because it highlights the need to consider breathing effectiveness as well as the surrounding gas and pressure. Anyone with symptoms or a medical concern related to diving should consult a diving-medicine physician; this general information is not individual medical advice.

Frequently asked questions

What is carbon dioxide toxicity?

It describes harmful effects associated with excessive carbon dioxide exposure or retention, which can affect breathing, acid–base balance and mental or physical performance.

Why can carbon dioxide build up during a dive?

Carbon dioxide can accumulate when ventilation does not adequately remove what the body produces. Workload, breathing pattern and equipment characteristics can influence this balance.

Who should seek advice about a diving-related concern?

A diver with symptoms or a medical concern connected to diving should consult a physician experienced in diving medicine.

Citation details

Title: Carbon Dioxide Tolerance and Toxicity
Authors: Lambertsen, CJ
Year: 1971
Published in: IFEM Report No. 2-71
Repository record: Rubicon Research Repository, handle 123456789/3861

This page is an original summary written by the Rubicon editors from the publication’s bibliographic record. It does not reproduce the paper, its abstract or its data; consult the publication itself for its methods and findings.