At a glance
The difference in one table
The protocols overlap in the experience of air hunger, but the timer captures a different performance in each test.
| Compare | CO₂ tolerance | BOLT |
|---|---|---|
| Task | One gentle, continuous controlled exhale | Pause after a normal exhale |
| Stop signal | When you need to inhale | At the first definite urge to breathe |
| Score | Controlled-exhale duration | First-urge hold duration |
| Best fit | Auralize’s default public calibration baseline | A familiar breath-hold protocol with a subtle stop rule |
| Conversion | None. Do not translate or compare raw seconds across the two tests. | |
Decision
Which test should you use?
Use the task you can repeat honestly. The important choice is not which score looks higher; it is which protocol matches what you want to track.
Start with CO₂ tolerance when…
You want the default Auralize assessment, prefer continuous breathing to a hold, or want the app to establish a starting pace from its controlled-exhale baseline.
Choose BOLT when…
You specifically want a post-exhale first-urge hold, already track BOLT elsewhere, or find that stopping rule easier to reproduce than a slow exhale.
Auralize may use either result as a product pacing input. That mapping is an internal training heuristic—not a validated clinical conversion and not evidence that the raw scores measure the same thing.
Protocol
How each assessment works
CO₂ Tolerance Assessment
- Complete the guided warm-up breaths while seated.
- Take the prompted gentle inhale.
- Exhale softly and continuously without squeezing.
- Stop when you need to inhale and return to normal breathing.
BOLT Breathing Assessment
- Complete the calm warm-up while seated.
- Take an ordinary nasal inhale and ordinary nasal exhale.
- Pinch the nose and pause after the exhale.
- Stop at the first clear urge—not your maximum hold.
Interpretation
What the numbers can—and cannot—tell you
BOLT is a timed first-urge breath hold. Its result can change with breathing pattern, recent activity, anxiety, airway comfort, and how consistently you notice the stopping signal. Despite the name, a browser-based BOLT test does not directly measure blood oxygen, arterial CO₂, or lung function.
Auralize’s CO₂ score is the duration of a controlled-exhale task. Starting lung volume, airflow, technique, respiratory mechanics, effort, and the decision to stop all affect it. “CO₂ tolerance” is a useful product label, not a blood-gas measurement.
A 30-second slow exhale is not a 30-second BOLT. There is no validated formula for converting between these Auralize protocols. Keep each score in its own history.
Retesting
Make the trend more useful
Repeat the same protocol at a similar time of day, in the same posture, after a similar amount of rest. Avoid comparing a waking result with one taken after hard exercise, a heavy meal, or deliberate over-breathing. Record context and look for a multi-test trend instead of treating one attempt as a verdict.
Stay seated and away from water, driving, and other hazards. These are not maximum challenges. Stop for dizziness, chest discomfort, visual changes, severe breathlessness, or distress. Ask a clinician before breath-hold testing if you are pregnant, prone to fainting, or have a significant cardiovascular, neurological, or respiratory condition.
Evidence
What supports the guidance
The evidence supports careful, repeatable respiratory protocols and the physiology of slow breathing. It does not establish a direct conversion between these two consumer assessment scores.
Respiratory physiology
A review of slow breathing describes interactions among ventilation, chemoreflexes, baroreflexes, heart-rate variability, and respiratory mechanics. Read the review.
Measurement limits
For the mechanics, citations, and limits behind Auralize’s consumer protocols, read the evidence deep-dive.
Questions
Frequently asked
Is the BOLT test the same as a CO₂ tolerance test?
No. BOLT times a pause after a normal exhale until the first definite urge to breathe. Auralize’s CO₂ assessment times one continuous, controlled exhale. They use different tasks and their raw scores are not interchangeable.
Which assessment should I take first?
Start with the CO₂ Tolerance Assessment if you want the default Auralize baseline used to suggest a starting breathing pace. Choose BOLT if you specifically want a post-exhale, first-urge breath-hold protocol.
Can I convert a BOLT score into a CO₂ tolerance score?
No validated conversion exists between the two Auralize protocols. Compare a result only with your own previous results from the same test under similar conditions.
Do I need an account to take either test?
No. Both guided assessments can be started without signing in.