Model O vs AirGradient ONE: Which Indoor Air Quality Monitor Fits Your Deployment?
Short answer: both measure CO2, particles, VOC, NOx, temperature and humidity. Choose Model O for wired Ethernet, optional PoE, barometric pressure and 48 months of one-minute cloud history. Choose AirGradient ONE when a built-in display is important. Either can support a local smart-home workflow.
Reading Time: 8 minutes
Model O and AirGradient ONE at a glance
| Feature | VisiblAir Model O (2026) | AirGradient ONE (Gen 9) |
|---|---|---|
| Measurements | CO2; PM1, PM2.5, PM4, PM10; VOC Index; NOx Index; temperature; humidity; pressure | CO2; PM1, PM2.5, PM10; VOC/TVOC; NOx Index; temperature; humidity |
| CO2 sensor | Sensirion SCD30 NDIR | Senseair S8 or S88 NDIR |
| Published CO2 accuracy | ±(30 ppm + 3% of measured value) at 25 °C from 400–10,000 ppm | ±(40 ppm + 3% of reading) under the temperature, humidity and concentration conditions documented for the installed S8 or S88 |
| PM sensor | Sensirion SEN55 | Plantower PMS5003 |
| VOC and NOx sensor | Sensirion SEN55 | Sensirion SGP41 |
| Network | 2.4 GHz Wi-Fi or wired Ethernet | 2.4 GHz Wi-Fi; Bluetooth LE hardware is listed |
| Power | USB-C or optional PoE | USB-C; 5 V, 2 A adapter required and not included |
| On-device display | No; readings are available through the local page, local API or cloud portal | 1.3-inch OLED display and 11-LED status bar |
| Cloud history | 48 months at sampling intervals as short as one minute | Raw unbucketed data: 10 days; 5-, 10- and 30-minute data: 150 days; hourly or coarser data: currently retained indefinitely |
| Local access | Local readings page and local API, including Home Assistant integrations | Cloud-independent local JSON API and native Home Assistant discovery |
| Repair path | The combined SEN55 PM/VOC/NOx module is easily replaceable | Individual sensor modules are replaceable |
| Published certifications | No product certifications listed on the current product page | RESET Air, CE, FCC, RoHS and REACH listed for the assembled model |
| Dimensions | 138 × 139 × 33 mm | 131.2 × 131.2 × 36.2 mm and 230 g in the I-9PSL-DE specification sheet |
| Warranty | 12 months | 12 months for the assembled model |
| Base price checked September 15, 2026 | CAD $289 | About CAD $320 assembled (USD $230); about CAD $192 for the uncertified DIY kit (USD $138) |
The AirGradient conversions use the Bank of Canada's September 15, 2026 indicative daily average of CAD $1.3917 per US dollar and are rounded to the nearest dollar. Prices exclude options, shipping, taxes, duties, import fees and foreign-exchange charges.
Where Model O differs: Ethernet, PoE and pressure
Both standard models can join a 2.4 GHz Wi-Fi network, but Model O also provides wired Ethernet. Selecting its PoE option lets one Ethernet cable carry both data and power. This is useful where facilities teams want fixed cabling, where Wi-Fi coverage is inconsistent, or where IT prefers sensors on managed wired infrastructure.
Model O also reports barometric pressure and PM4. AirGradient ONE does not list either measurement. Both monitors require continuous external power, so neither is the right choice for battery-powered surveys or portable spot checks.
Cloud history and local access
The VisiblAir Cloud Portal retains 48 months of readings at sample intervals as short as one minute. It provides fleet status, graphs, exports, API access, sharing and configurable threshold and offline-sensor alerts. Cloud access is free for up to 10 sensors on an account; each additional sensor is currently CAD $5 per month or $50 per year plus tax.
AirGradient documents a different retention model: 10 days for unbucketed data, up to 150 days for 5-, 10- and 30-minute buckets, and indefinite retention for hourly or coarser buckets. Its product page calls the dashboard subscription-free, but the assembled-product list also says that 12 months of dashboard and API access are included. Buyers planning a long-term fleet should confirm the post-year terms directly with AirGradient.
For local integrations, either monitor can work. Model O provides a local readings page and local API, with Home Assistant as a supported integration path. AirGradient ONE provides a cloud-independent local JSON API, native Home Assistant discovery and other documented integrations.
What the PM2.5 accuracy figures do—and do not—say
These are manufacturer claims made at different levels: Plantower describes its component, while AirGradient describes an assembled and corrected monitor. They are not an independent head-to-head result. Model O publishes ±10 µg/m³ from 0–100 µg/m³ and ±10% from 100–1,000 µg/m³ for its SEN55-based PM readings.
Display, repairability and platform choices
AirGradient ONE has the clearer at-a-glance interface: its OLED screen shows current values and its RGB LED bar can indicate status. Model O has no physical display and is intended to be read through its local page, API or cloud portal.
Both products have a practical repair path. AirGradient documents a modular design with individually replaceable sensor modules. Model O's combined Sensirion SEN55 module, which measures PM, VOC and NOx, is also easily replaced. AirGradient additionally publishes its hardware and firmware under an open licence; Model O's current product materials do not make an equivalent open-source claim.
CO2 calibration strategy
VisiblAir ships its CO2 monitors with automatic baseline calibration disabled. A monitor in a continuously occupied or mechanically controlled room may not regularly reach a known fresh-air reference, so treating the lowest recurring reading as outdoor background can introduce bias. VisiblAir recommends periodic checks and manual recalibration when needed.
AirGradient documents seven-day automatic baseline calibration for its Senseair CO2 sensor. The interval can be changed or the feature disabled. This can suit rooms that reliably reach a valid outdoor-air baseline; otherwise, the setting should be reviewed for the deployment.
Which monitor fits which use case?
| Use case | Better fit | Reason |
|---|---|---|
| Fixed office, school or commercial deployment with Ethernet | Model O | Wired Ethernet and optional PoE can simplify permanent installations |
| Pressure or PM4 monitoring | Model O | Those measurements are included |
| Four years of one-minute cloud history | Model O | 48-month retention is included in the portal |
| Local-first smart home or self-hosted workflow | Either | Both offer local APIs and Home Assistant paths; AirGradient documents native discovery and fully cloudless operation |
| Reading values without a phone or browser | AirGradient ONE | Built-in OLED display and LED status bar |
| Project requiring the listed certifications or RESET Air accreditation | AirGradient ONE | AirGradient publishes the relevant documents |
| Battery-powered or outdoor monitoring | Neither | Use a purpose-built portable or outdoor monitor |
Sources and comparison limits
This article compares published specifications, not readings collected side by side. Accuracy formulas use different conditions and cannot establish which complete monitor will perform better in every room. Gas indexes show changes relative to a learned background; they do not identify a specific chemical or replace a regulatory gas analyzer.
- VisiblAir: Model O product page, August 2026 product update, CO2 auto-calibration guide, and VOC Index guide.
- AirGradient: AirGradient ONE product page, Generation 9 specification sheet, dashboard retention documentation, and certification documents.
- PM context: Plantower PMS5003 specification and AirGradient calibration explanation.
- Currency: Bank of Canada daily exchange rates.
AirGradient's product page and downloadable sheet disagree on dimensions and weight. This article uses the model-specific I-9PSL-DE sheet. Specifications, pricing, exchange rates, cloud policies and certifications can change; verify the linked sources before purchasing.
Plan a connected indoor deployment
Model O combines CO2, PM, VOC, NOx and pressure sensing with Wi-Fi, wired Ethernet, optional PoE, a local API and four years of detailed cloud history.