By Justin Carlson. Sources checked November 7, 2026. Documentation review only; not tested hands-on.
The AirGradient ONE (I-9PSL) is a Wi-Fi indoor monitor that you can read directly on your own network as well as through AirGradient’s cloud dashboard and API. It suits small projects and technically comfortable buyers who want current readings without depending on a vendor account. The central tradeoff: the local endpoint returns only current values, so history either comes from the cloud API (in limited windows) or from your own logging.
Best fit and when it may not suit you
Good fit
A handful of rooms where someone can poll the monitor on the local network and store readings themselves.
Home Assistant, MQTT or open-firmware projects that prefer documented, inspectable hardware.
Pilots that need true NDIR CO2 and particulate data at a published hardware price.
May be unsuitable
Buyers who need a contracted SLA, procurement paperwork or a vendor-managed multi-site rollout: none was documented in the sources reviewed.
Sites without 2.4 GHz Wi-Fi, unless the separately listed cellular variant is confirmed for your region.
Projects that need absolute VOC or NOx concentrations: the monitor reports Sensirion index values.
What this profile covers
Hardware
AirGradient ONE indoor monitor, model I-9PSL (9th generation); cellular variant I-9PSL-CE listed separately
Platform
Direct local HTTP access on the monitor, plus the AirGradient Dashboard and its cloud API
Plan
No named paid plan found. The product page calls the dashboard subscription-free; the same page lists 12 months of dashboard and API access for the assembled unit (see discrepancies).
Scope
Consumer and small projects. Sold to individuals, schools and small organizations. Nothing reviewed describes an enterprise contract, SLA or fleet-management tier.
Capabilities apply to this setup only. Other AirGradient products may differ.
AirGradient measurements and units
Parameters reported by AirGradient ONE
Parameter
Type
Unit
Models
Notes
CO2
Measured
ppm
I-9PSL
SenseAir S8 NDIR sensor (0–10,000 ppm per spec); reported as rco2. [1, 4]
PM1, PM2.5, PM10
Measured
µg/m³
I-9PSL
Plantower PMS5003 laser scattering sensor. The cloud API also exposes a corrected PM2.5 field. [1, 3]
TVOC
Index (relative)
VOC Index (0–500)
I-9PSL
Sensirion SGP41. The vendor describes it as relative change, not a concentration. A raw signal is also exposed locally; the spec mentions a ppb option without detail. [1, 4]
Available AirGradient ONE I-9PSL, sold assembled or as a kit with the same hardware. [1]
Gateway or hub
Not applicable No gateway is described; the monitor connects over Wi-Fi itself. [1]
Network
Available 2.4 GHz Wi-Fi (802.11 b/g/n). A cellular model, I-9PSL-CE, is listed as an alternative. Condition: A 5 V / 2 A USB power supply is required and not included. [1]
Account
Conditional Not needed for the local endpoint. The cloud API token comes from an AirGradient Dashboard account. [2, 3]
Subscription
Unknown The product page says the dashboard is subscription-free; the same page lists “12 months” of dashboard and API access. What applies after 12 months is not stated. [1]
Local access, cloud API and export
In practice there are two separate paths. On your own network, any script can request the monitor’s current readings as JSON without an account, as long as the firmware is recent enough. That is ideal for a dashboard on a wall or a home-automation system, but nothing is stored unless you store it.
The cloud path runs through AirGradient’s dashboard. Once API access is enabled for a place, a token lets you request current values and history in windows of up to 10 days. MQTT and Home Assistant are further options that push or pull readings locally. Opting in to the public map is a separate choice and is not needed for any of these.
Local access
Conditional HTTP GET /measures/current on the monitor’s local hostname returns current readings as JSON; /config reads and writes settings. No dashboard token is needed. Condition: Firmware 3.0.10 or later; client on the same network. [2, 4]
Cloud API
Conditional REST API at api.airgradient.com with current, past (5- or 60-minute buckets) and raw-measure endpoints per location. Condition: API access must be enabled in dashboard settings to obtain a token. The assembled unit lists 12 months of dashboard and API access; terms after that are not stated. [2, 3]
Manual export
Not publicly documented No dashboard CSV export procedure was found in the documentation reviewed. [2, 1]
Other protocols
Available MQTT (broker URL in local config), native Home Assistant support (2024.6+ with current firmware), Homey; community ESPHome, Prometheus and openHAB integrations. A Modbus specification article is listed but was not reviewed. [1, 4]
AirGradient API details
Authentication
Available Cloud: per-place access token passed as a “token” query parameter. Local: no authentication is documented. [3, 4]
Who can access which data
Available The token is issued for a place and returns that place’s private data. Some world/public endpoints need no token and return only data owners chose to share. The public indoor dataset is opt-in, and indoor coordinates are rounded to one decimal place before publication. [3, 2, 5]
Latest versus historical data
Conditional Local endpoint: current values only. Cloud: current measures, past measures limited to 10 days per request, and the most recent 200 raw records (2-day window). [4, 3]
Retention
Not publicly documented No cloud retention period is stated in the API specification or pages reviewed. [3, 1]
Sampling and aggregation
Conditional Cloud history is returned in 5-minute or 60-minute buckets “depending on what is available”. [3]
Timestamps and timezone
Available ISO 8601 with UTC offset (e.g. 2022-03-28T12:07:40Z); request parameters use basic format (20220328T120500Z). [3]
Rate limits
Not publicly documented No numeric rate limit appears in the published API specification. [3]
Export formats and limits
Conditional JSON via local and cloud APIs. No file-export format is documented in the sources reviewed. [3, 4]
Multiple devices and sites
Conditional The cloud API is organized by place and location IDs and offers averaged buckets across several locations. No enterprise fleet tooling was documented. [3, 2]
Integrations
Available Home Assistant, Homey, MQTT and community integrations; firmware and hardware designs are open source (CC-BY-SA 4.0). [1]
Usage and reuse restrictions
Restricted by terms A terms summary says owners own their monitor data, but the full terms restrict reselling or commercially exploiting “the services” without defining whether API output is included. The public dataset requires keeping provider, source and licence metadata when redistributed. [6, 7, 5]
AirGradient pricing: hardware, platform and API
Prices are shown only where the vendor publishes them, as checked on November 7, 2026. Taxes, shipping and implementation work are not included.
AirGradient ONE cost components
Component
Item
Status
Price and basis
Notes
Hardware
AirGradient ONE, fully assembled and tested
Published price
USD 230.00, one-time, per monitor (Region not stated on page)
The local endpoint returns current values only. To keep history without the cloud, you must poll and store readings yourself.
VOC and NOx are relative index values from the Sensirion SGP41, not concentrations.
Cloud past-measure requests are capped at a 10-day window, so long backfills need many requests; no rate limit or retention period is published.
No dashboard CSV export procedure was found in the sources reviewed.
Conflicting or unclear documentation
The product page calls the dashboard “subscription free”, but the assembled-unit listing includes “12 months data platform / dashboard and API access”. What happens after 12 months is not stated. The pricing page did not load during review. [1]
Temperature/humidity sensor is listed as SHT40 in the spec table and SHT3x/4x in page text. CO2 auto-baseline is “every seven days” on the product page and “Default 8 days” in the local configuration docs. [1, 4]
A short terms summary says “YOU own the data from your monitor”, while the full terms contain broader restrictions on commercial exploitation of the services. [6, 7]
Not yet answered by public documentation
What dashboard and API access remains after the first 12 months, and at what price?
Is there a dashboard CSV export, and how far back can it go?
What rate limits and data retention apply to the cloud API?
Does the cellular I-9PSL-CE variant expose the same local endpoint?
Before requesting a quote
Ask AirGradient in writing what dashboard and API access costs after month 12.
Confirm the firmware version that will ship and that /measures/current is enabled on it.
Decide who will run the poller and database if you rely on local access for history.
Confirm whether you need absolute VOC concentrations; the ONE reports an index.
If reusing data commercially, ask whether API output counts as “the services” under the terms.
These are ordinary links to the manufacturer. The editor, Justin Carlson, co-founded and leads Invivus Technologies, which runs Moldmap, SensiReport and Moldlist and is developing Aerlume, an indoor mold sensor. He has no financial relationship with AirGradient, Airthings, Atmocube or Kaiterra, no vendor pays for coverage or placement, and the site has no affiliate links. Indoor Air API Guide does not provide manufacturer support.
Local server API (firmware documentation), AirGradient firmware repository (documentation). Checked November 7, 2026. Linked from AirGradient’s knowledge base via github.com/airgradienthq/arduino, which now resolves to this repository.