Ethylene is the ripening hormone. Climacteric fruits produce it themselves and respond to it — a relationship that has governed storage practice for decades. The practical question is not whether ethylene can be measured, but from which concentration you need to see it. And the answer spans more than four orders of magnitude depending on the task.
We put the numbers first because they decide suitability. For ethylene, NZGS 2 has a limit of detection warranted in the datasheet of 400 ppb, that is 0.4 ppm.
| Situation | Ethylene concentration | NZGS 2, 400 ppb warranted |
|---|---|---|
| Ripening room, deliberate gassing | 100–150 ppm | far above — clearly detectable |
| Storage of climacteric fruit, measured | 0.014–4.9 ppm | upper part of the range detectable |
| Triggering irreversible ripening | 0.1–1.0 ppm | partly, from 0.4 ppm |
| General threshold for ethylene action on plants | from about 0.1 ppm | below the limit of detection |
| Recommendation for sensitive produce | below 0.005 ppm | roughly 80× below — not detectable |
400 ppb equals 0.4 ppm. The warranted value comes from datasheet rev. 3.3.0, determined at 25 °C and 45 % relative humidity. The storage concentrations are horticultural working figures from the literature and vary with cultivar, temperature and storage duration.
That boundary sits deliberately near the top of this page. A sensor installed in the wrong application creates confidence in a measurement that is not happening — and with stored produce that costs more than no measurement at all.
For deliberate ripening, ethylene is used at concentrations around 100 to 150 ppm; for tomatoes roughly 100 ppm over about 48 hours. That is two and a half orders of magnitude above the limit of detection.
What matters here is not sensitivity but reliability over time. A ripening room is warm, humid and full of volatile compounds from the produce itself. The sensor has to stay stable under those conditions and must not respond to every other gas that happens to be forming.
A store full of fruit is anything but quiet in gas-chemical terms. Ripening and over-stored produce releases:
A sensor that outputs only a sum reading sees a rising curve and cannot say whether the produce is ripening or spoiling. Yet that is exactly the distinction that matters: ripening is wanted and controllable, spoilage is a loss.
NZGS 2 carries four sensing elements on a die of 1.15 × 1.15 mm. Because each element has a different layer and a different operating temperature, one gas event produces four different signal traces, and the substance is determined from the ratio between them. How that works in detail is on the technology page.
For ethanol the datasheet warrants a limit of detection of 30 ppb. That is more than an order of magnitude more sensitive than for ethylene, and it lies in a range where incipient fermentation becomes detectable before it is visible or noticeable by smell.
In practice this is the more interesting channel. Ethylene says produce is ripening — which it does anyway, and usually as planned. Ethanol says something is going wrong: too little oxygen, too warm, a damaged batch. Together the two give a picture that neither value provides alone.
The same arithmetic applies in containers and trailers, under harder conditions: tight installation space, vibration, changing temperature and humidity, no maintenance access in transit. Form factor and power consumption co-decide here — a component in QFN-8 at 2.8 × 2.8 × 1.6 mm drawing around 70 mW can be accommodated; a laboratory instrument cannot.
Humidity deserves attention. The permitted operating range extends to 90 % relative humidity, non-condensing. In a refrigerated container that is a real boundary condition, not a formality: temperature and humidity belong in the measurement, because both shift the signal and compensation otherwise has no data basis.
Large cold stores frequently use ammonia as a refrigerant. Ammonia is detected by NZGS 2, but the datasheet warrants no limit of detection for it. Measured values and test conditions can be determined on a project basis.
At the outset stands the question of whether the target substances separate cleanly for your produce and your storage conditions. That cannot be derived from specifications, only measured. The evaluation kit with read-out electronics and software exists for this: it records the four signal traces, extracts the features and shows whether the target substances form separate regions in feature space.
What gets recorded is reference air for the baseline, the target substances at known concentrations, and the interferents that realistically occur in the store — plus the boundary conditions temperature and humidity across the expected range. All specifications of the component are in the datasheet extract.
Tell us what you store and in which concentration range you need to measure. If 400 ppb is too coarse for your application we will say so — and tell you what to consider instead.
Send an enquiryStorage and ripening concentrations after horticultural literature and postharvest practice; sensor characteristics after NANOZ NZGS 2, datasheet rev. 3.3.0.
