# CO2 sensor vs Thermometer

The clearest difference is rating: Thermometer at 4.5 against CO2 sensor's 3.4. Thermometer also leads on update cadence (monthly vs every 12 months) and ratings volume (394 vs 7). CO2 sensor's advantage is ads (none vs shown) and monetization model (free vs free with in-app purchases). On price, in-app purchases and iOS requirement there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

Thermometer holds the better App Store score, 4.5 against 3.4. That said, the two scores are not equally well evidenced: Thermometer has 394 ratings behind it against 7, so its average is the more settled of the two.

CO2 sensor ships an update every 12 months, Thermometer monthly. The most recent releases landed on November 3, 2026 and October 30, 2026 respectively.

## The numbers

| Metric | CO2 sensor | Thermometer |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [3.4 (7 ratings)](https://appshunter.io/ios/app/co2-sensor/id1643286074/reviews) | **[4.5 (394 ratings)](https://appshunter.io/ios/app/thermometer-room-and-indoor-track/id6748902003/reviews)** |
| Number of ratings | 7 | **394** |
| Positive reviews | — | 65.4% of reviews |
| In-app purchases | No | No |
| Ads | **No** | Yes |
| Update frequency | Every 12 months | **Monthly** |
| Monetization | **Free** | Free with in-app purchases |
| Size | 0 MB | 5 MB |
| Requires iOS | **15.6** | 16.6 |
| Devices | **iPhone, iPad, iPod, Mac** | iPhone |
| Age rating | 4+ | 4+ |
| Developer | [sighmon](https://appshunter.io/developer/377815161) | [梦楠 牛](https://appshunter.io/developer/1825512596) |

## What reviewers say

### CO2 sensor

[App page](https://appshunter.io/ios/app/co2-sensor/id1643286074)

Monitor CO2, temperature, and humidity levels in real-time using a Bluetooth sensor. Save readings with location data and sync them across Apple devices via iCloud. View historical data on a map.

**Highlights:** Real-time CO2, temperature, and humidity readings, Bluetooth sensor integration, Save readings with location, iCloud sync across devices, Map view of saved readings, Open source code available

**Features:** Vision Pro support

**In-app purchases:** none


### Thermometer

[App page](https://appshunter.io/ios/app/thermometer-room-and-indoor-track/id6748902003)

Monitor indoor and outdoor temperatures in real time with detailed historical data and trend charts. Track temperatures from multiple locations simultaneously and access basic environmental data and converters.

**Highlights:** Real-time temperature tracking, Historical data and trend charts, Multi-location monitoring, Environmental data, Unit converters

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none

**What reviewers like**

- 👍 Great app
- 👍 Good
- 👍 App I've been waiting for

**What reviewers complain about**

- 🔒 Requires 5-star review to unlock features
- 🔒 Forces review before using app
- 🐛 Gives outside temperature instead of room temperature
- 🐛 Constant ads

**Reported bugs**

- Gives incorrect temperature information
- Crashes or freezes

**Requested features**

- Allow users to provide reviews without forcing 5-star ratings


## Frequently asked questions

### Is CO2 sensor free?

CO2 sensor is free to download, with no in-app purchases.

### Is Thermometer free?

Thermometer is free to download, with no in-app purchases.

### Which has better reviews, CO2 sensor or Thermometer?

Thermometer is rated higher. CO2 sensor averages 3.4 out of 5 from 7 ratings, while Thermometer averages 4.5 from 394 ratings.

### Do CO2 sensor or Thermometer have ads?

Thermometer shows ads; CO2 sensor does not.

### Which is updated more often, CO2 sensor or Thermometer?

CO2 sensor ships an update every 12 months, and Thermometer monthly. Most recently, CO2 sensor was updated on November 3, 2026 and Thermometer on October 30, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*