CO2 sensor vs Census Scan
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
CO2 sensor
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.
- 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
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Read CO2, temperature, and humidity from your Bluetooth Sensirion SCD-41 sensor in realtime. Save your readings with your current location and have it sync across your devices via iCloud. See previously saved readings with a map of the location that those readings were taken. Works across iPhone, iPad, and macOS devices. Open source code: https://github.com/sighmon/ios-ble-co2-sensor
Census Scan
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Your Australian Census letter holds the two things you need to log in: a 16-digit Census number and a 9-character temporary password. Census Scan reads them with your camera and opens the official Census website — census.abs.gov.au, run by the Australian Bureau of Statistics (ABS) — with both fields typed in for you. Check the numbers, press Next on the page, and get on with your Census. WHY WE MADE THIS Could the Census have been an easier process? We think so. Logging in means reading 25 random letters and digits off a printed page and typing them without a slip. The letter prints them in spaced groups — which helps you read them, but plants a doubt: do you type the spaces or not? The temporary password mixes lowercase letters and digits that are easy to confuse — is that a lowercase L or a one? An O or a zero? Not everyone finds 25 characters of that easy to read, let alone enter correctly on a phone keyboard. A QR code on the letter would have solved it — everyone knows QR codes. There isn't one. So we built the missing piece: an app that does the reading and the entering for you. HOW IT WORKS 1. Point your camera at Step 2 of your Census letter. 2. Check the two values it read. Tap to correct anything. 3. The official website opens with your details filled in. Press its Next button and complete your Census there, exactly as normal. That is the whole app. Once the website is open, Census Scan's job is done. PRIVATE BY DESIGN • Nothing is recorded. The camera feed is read on your phone by Apple's built-in text recognition. No photo or video is saved. • Nothing is stored. Your details are held in memory just long enough to fill in the login page, then vanish. No accounts, no analytics, no tracking, no third-party code. • Nothing is sent anywhere except the official ABS website — the same page your letter tells you to visit. • Open source. The complete source code is public, so anyone can verify every one of these claims: github.com/agenta-consulting/census-scan Census Scan is a free community tool made by Agenta. It is not affiliated with, or endorsed by, the Australian Bureau of Statistics.
Screenshots
Verdict
The clearest difference is update cadence: Census Scan at daily against CO2 sensor's every 12 months. CO2 sensor's advantage is device support (4 vs 1) and iOS requirement (15.6 vs 17.0). On price, ads and in-app purchases there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
CO2 sensor ships an update every 12 months, Census Scan daily. The most recent releases landed on October 24, 2026 and October 25, 2026 respectively.
| Parameter | CO2 sensor | Census Scan |
|---|---|---|
| Price | Free | Free |
| Rating | 3.4 (7 ratings) — better | — |
| Number of ratings | 7 — better | — |
| Update frequency | Every 12 months | Daily — better |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Free | — |
| Devices | iPhone, iPad, iPod, Mac — better | iPhone |
| Requires iOS | 15.6 — better | 17.0 |
| Further details — not scored | ||
| Size | 0 MB | 1 MB |
| Age rating | 4+ | 4+ |
| Developer | sighmon | Keith Rowell |
In-app purchases
CO2 sensor
No in-app purchases
Census Scan
No in-app purchases
Questions
Is CO2 sensor free?
Is Census Scan free?
Do CO2 sensor or Census Scan have ads?
Which is updated more often, CO2 sensor or Census Scan?
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