Model C vs Aranet4: How Closely Do Their CO2 Readings Agree?
Short answer: in this 16-hour, side-by-side run, Model C tracked the Aranet4 very closely. Their 962 paired readings had a 0.991 correlation, a 15 ppm median absolute difference, and the same manufacturer-stated CO2 accuracy formula.
Reading Time: 7 minutes
What the side-by-side data shows
| Result | Observed value | What it means |
|---|---|---|
| Paired collection rows | 962 over 16.0 hours | No CO2 values were missing from either series |
| Observed range | Aranet4: 503–2,423 ppm Model C: 520–2,839 ppm | The run included both relatively fresh air and elevated indoor CO2 |
| Pearson correlation | 0.991 | The two devices followed the same overall rises and falls very closely |
| Median absolute difference | 15 ppm | Half of paired readings differed by no more than 15 ppm |
| Mean absolute difference | 28.4 ppm | The average size of the paired difference, ignoring direction |
| Pairs within 30 / 50 ppm | 79.1% / 91.2% | Most row-paired observations were tightly grouped |
| Mean signed difference | Model C +16.8 ppm | Model C averaged slightly higher; this does not identify which device was closer to the true concentration |
How the comparison was calculated
The source recorded each device about once per minute from September 13 at 20:17 UTC to September 14 at 12:18 UTC. Each collection row pairs the most recent Model C and Aranet4 values. Model C samples were timestamped an average of 34.5 seconds earlier than the Aranet4 samples, so short-lived peaks can create larger row-by-row differences even while the overall curves agree.
The correlation uses the 962 row-paired CO2 values. Absolute-difference statistics use |Model C − Aranet4|. The chart uses each device's own sample timestamp. Download the CO2-only comparison data (CSV). The committed generator at script/generate_co2_comparison.py reproduces the calculations, public dataset, and chart from the original source CSV.
Does this show that Model C is as good as Aranet4?
Yes—in this run, Model C delivered CO2 tracking that was at least comparable to the Aranet4. A 0.991 correlation, a 15 ppm median absolute difference, and 91.2% of pairs within 50 ppm are practical evidence that this Model C unit followed this Aranet4 unit closely across a wide changing range. The published specifications also give both products the same nominal accuracy expression: ±(30 ppm + 3% of reading), within each manufacturer's stated conditions.
Model C and Aranet4 feature comparison
| Feature | VisiblAir Model C | Aranet4 HOME |
|---|---|---|
| CO2 sensing | Sensirion SCD30 dual-channel NDIR | NDIR |
| Published CO2 range | 0–10,000 ppm; accuracy stated from 400–10,000 ppm | 0–9,999 ppm; standard accuracy stated from 0–5,000 ppm under documented environmental conditions |
| Published CO2 accuracy | ±(30 ppm + 3% of reading) | ±(30 ppm + 3% of reading); 10% above 5,000 ppm is extrapolated and not guaranteed |
| Display | E-ink | E-ink with colour status indicator and optional buzzer |
| Connectivity | 2.4 GHz Wi-Fi | Bluetooth to a nearby phone or tablet |
| History and access | Cloud history, CSV export and API access; remote access from an internet connection; stores readings during Wi-Fi interruptions and synchronizes later | Aranet Home app charts and exports with up to 90 days of history, depending on settings; direct access requires Bluetooth range |
| Monitoring multiple devices | Cloud access is free for up to 10 sensors in one account | Multiple compatible sensors can be viewed in the Aranet Home app |
| Origin and shipping source | Engineered, assembled, and tested in Québec, Canada; built to order and shipped from Canada | Produced in Latvia, Europe, according to manufacturer SAF Tehnika; a direct-store purchase delivered to Canada is an international order |
| Power | Rechargeable internal battery plus 5 V USB-C; can remain plugged in for continuous monitoring | Two replaceable AA batteries; manufacturer advertises up to four years depending on settings and battery type |
| Warranty | 1 year | 2 years, extendable to 3 through manufacturer registration |
| Canadian price checked September 14, 2026 | CAD $209 plus shipping calculated at checkout | CAD $239 plus CAD $10 shipping, before applicable import fees |
Features and prices can change. Model C details come from the current product page and VisiblAir portal documentation. Aranet4 specifications come from the manufacturer's product page, datasheet, and app documentation. SAF Tehnika's company information identifies its products as produced in Latvia, Europe. The Aranet direct-store price, shipping, and import-fee terms are the checkout values supplied for this comparison.
Why Model C is the stronger connected choice
Model C combines closely comparable CO2 readings with a broader connected-monitoring package. Its rechargeable battery supports portable checks without disposable batteries, while USB-C power makes it ready for continuous operation. Wi-Fi cloud access works without keeping a phone nearby, readings survive temporary Wi-Fi outages, and multiple rooms can be reviewed remotely in one portal. Its CAD $209 list price is also $30 below the supplied Aranet4 list price.
For Canadian buyers, Model C is the local choice: it is engineered, assembled, tested, and shipped from Québec, so a domestic order does not cross an international border before delivery. The Aranet4 is produced in Latvia and the supplied direct-store checkout adds CAD $10 shipping plus applicable import fees. Final totals still depend on taxes and the selected Model C shipping option.
Aranet4 HOME's clearest advantage is multi-year operation on replaceable AA batteries. For buyers who value remote access, rechargeable portability, automatic cloud synchronization, longer-term centralized history, CSV/API data access, and a lower list price, Model C offers the stronger overall value. This dataset reinforces that choice by showing that Model C's CO2 readings tracked the Aranet4 very closely throughout the 16-hour run.
Choose connected CO2 monitoring
Model C combines a dual-channel NDIR CO2 sensor, E-ink display, Wi-Fi, outage buffering, and cloud history for homes, offices, and classrooms.
