Why ZoneX focuses on a single reliable measurement: ventilatory thresholds (VT1/VT2)
- PAIRFS
- 2 days ago
- 4 min read
And how does this fit into the long-term vision of a portable CPET?
In endurance sports, breathing is one of the most powerful physiological signals. Yet, measuring respiratory gases remains a complex field, dominated by cumbersome, expensive systems reserved for laboratories.
At PAIRFS, we want to change that: to make key metabolic information accessible to all athletes , on the field, during training.
But to achieve this, one fundamental rule must be respected:
👉 Don't measure everything until you can measure everything correctly.
This is the philosophy behind ZoneX.
1. Measuring respiratory gases: a major technological challenge
Measuring CO₂, ventilated volume and exhaled O₂ is extremely demanding.
Current CPET systems:
cost around €35,000
require regular maintenance (calibration, filters, tubing),
only function in controlled environments,
are incompatible with actual training (humidity, movement, external conditions).
Existing CO₂ or O₂ sensors on the market are not designed for respiration, neither at rest nor during strenuous activity. Humidity, rapid respiratory cycles, condensation, temperature variations, and pressure changes related to respiratory intensity all significantly disrupt the measurement.
No portable sensor on the market today can claim to offer reliable gas analysis in the field.
2. PAIRFS is building its own technology — with CEA LETI
To overcome these limitations, PAIRFS has undertaken long-term R&D work, in partnership with CEA LETI , one of the world leaders in micro-sensors.
This program ultimately aims for an ambitious goal:
👉 develop unique gas sensing technology to enable truly portable, reliable and field-adapted CPET .
This vision is already supported by a portfolio of 11 patents , covering in particular:
the stability of gas measurements,
the miniaturization of micro-sensors,
the resistance of the components to humidity,
signal processing approaches adapted to respiratory physiology.
But for these technologies to reach the expected level of precision, several more years of R&D , field testing and scientific validation will be needed.
3. ZoneX: a first product deliberately focused
In this long-term vision, ZoneX represents a first strategic step .
Rather than attempting to replicate a complete CPET — and risking providing incomplete or misleading data — ZoneX focuses on a single critical piece of information , achievable with absolute reliability:
👉 the ventilatory thresholds VT1 and VT2 .
Why them?
Because VT1 and VT2 do not require an absolute perfect measurement of the gases.
They rely on detectable transitions in:
the evolution of the expired volume,
the dynamics of CO₂ elimination,
changes in respiratory pattern.
These are robust , reproducible and physiologically clear markers.
But this is only made possible thanks to one of the key technological building blocks of PAIRFS:
👉 a gas sensor calibration technology specifically designed to remain stable despite humidity , a major problem in exertional breathing.
This innovation—at the heart of several PAIRFS patents—prevents the sensor from becoming uncalibrated during physiological testing and provides an accurate measurement of CO2 concentration.
It is this robustness that makes possible a reliable and repeatable measurement of ventilatory thresholds — and therefore a first product that is immediately useful to athletes.
4. A simple approach: measure less, but measure accurately
While many sports sensors scatter their efforts across a multitude of approximate metrics, ZoneX takes the opposite approach:
✔ Measure only what is reliable,
✔ to have complete control over the information delivered,
✔ to provide a solid foundation for training.
The goal is not to increase the sensor's capabilities too quickly. The goal is to gradually build a tool that will become, step by step, a true portable laboratory.
5. The long-term vision: a portable, but reliable CPET
ZoneX is just the beginning.
PAIRFS is moving towards a future where every athlete will have access to:
to a continuous measurement of VO₂,
monitoring of O₂ consumption in the field,
to a complete CO₂ analysis,
to an accurate reading of the minute ventilation,
to a complete CPET system… in a portable device.
But this future can only be built by respecting one fundamental requirement:
👉 Never sacrifice precision for quantity.
Conclusion
ZoneX embodies a simple yet powerful idea: performance is built on reliable data, not on an accumulation of uncertain measurements.
By focusing on ventilatory thresholds — the most useful and robust metric for endurance — PAIRFS lays the technological foundation for a next-generation portable CPET.
One sensor, one physiological truth, one perfectly reliable measurement.
That's the ZoneX philosophy.
A few references:
Wei, P. et al. (2018) – Impact Analysis of Temperature and Humidity Conditions on Electrochemical Sensors, Sensors. MDPI
Farquhar, A.K. et al. (2021) – Understanding and Correcting Unwanted Influences on the Response of Electrochemical Gas Sensors, ACS Sensors. PubMed
Samad, A. et al. (2020) – Effect of Relative Humidity and Air Temperature on the Performance of Low-Cost Gas Sensors, Sensors. MDPI
Martin, C.R. et al. (2017) – Evaluation and environmental correction of ambient CO₂ from low-cost NDIR sensors, Atmospheric Measurement Techniques. PMC
Ng, D.K.T. et al. (2025) – Environmental influences on NDIR CO₂ gas sensor using …, Sensors and Actuators B. ScienceDirect
Research progress of temperature and pressure compensation method of industrial environment gas sensor — Zhang H., Tian F. et al. (2025) ResearchGate+1
Research‑progress‑of‑temperature‑and‑pressure on Gas‐Sensors — H. Zhang et al. (2025), Physics of Fluids AIP Publishing
Comparatif capteur optique et capteur chimique: Hodgkinson, J. & Tatam, R. (2013). “Optical Gas Sensing: A Review.”
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