Product: PurpleAir Classic (PA-II)

Research date: 2026-09-23Worker C, air-quality monitorsDESK RESEARCH — no hands-on testing; owner evidence attributed.

Overview

Maker: PurpleAir (US). The original and most widely deployed PurpleAir sensor (PA-II). Indoor/outdoor particulate-matter monitor that feeds the crowdsourced PurpleAir real-time map. Outdoor-rated models carry two laser counters (Channels A/B).

Social standing

  • PurpleAir Users Group (Facebook) located via direct observation (facebook-cli groups search, 2026-09-23): named "PurpleAir Users Group", tool-reported member count ~2,000 (tool figure, not independently verified). Description frames it as a place to share information and experiences with PurpleAir sensors. Group posts read launched 2026-09-23 — held for security review, results pending at dossier write time.
  • PurpleAir community forum (community.purpleair.com) active: "how to get started" thread (July 2025, observed via search-index snippet 2026-09-23 — snippet-derived, not direct page read) with staff recommendations for indoor/outdoor picks.
  • Threads search ("PurpleAir air quality monitor", threads-cli, completed 2026-09-23, direct observation): 1 result — a Sept 20, 2026 promotional post from a competing open-source monitor brand, NOT PurpleAir owner content. No owner posts found in that result set.
  • Seed-file leads (May 2026 ozone/CO2/VOC buyer question; Sept 2026 poll/giveaway; Aug 2026 sensor troubleshooting threads) are UNRECOVERED as of 2026-09-23 — treated as UNVERIFIED, not cited as established.

Social validation: Tier 2

Named sources: (1) PurpleAir Users Facebook Group (direct observation, 2026-09-23) — proves active owner community; (2) PurpleAir community forum (snippet-derived, 2026-09-23) — proves setup/troubleshooting discussion and staff guidance; (3) independent tester BreatheSafeAir with hands-on Flex/Zen review incl. Classic in comparison table (snippet-derived, page updated ~July 2026). Weakness: no directly observed owner quotes in this pass.

Key specs

SpecDetailMeasured vs estimated
PM1.0 / PM2.5 / PM102× Plantower PMS5003 laser counters (Channels A/B)PM2.5: manufacturer + EPA research say good precision; PM10: manufacturer says NOT recommended (estimated from counts, low quality)
CO2None—
VOCNone—
RadonNone—
Temp / humidity / pressureNot on Classic (BME on Flex/Zen only)—
DisplayNone on device—
ConnectivityWiFi → PurpleAir real-time map; data stored/made available to smart devices; SD-logger edition (Classic SD) records without WiFi—
PowerUSB 5V (adaptor not included per retailer copy)—
Indoor/outdoorBoth (outdoor-rated)—

Pricing (dated 2026-09-23)

  • $229 — BreatheSafeAir comparison table (snippet-derived; review page updated ~July 2026). Consistent with airgradient.com's 2024 comparison ($229) — stale corroboration only.
  • Price history note: Institute for Energy Research doc cited older pricing context; not reused.
  • No current direct manufacturer-page price observed in this pass — flag for Stage 2.

What is included / what else is needed

Retailer copy (Checkmate product page, snippet-derived): sensor unit; power adaptor NOT included — needs outdoor-rated 5V USB adaptor. SD edition adds onboard logging.

Support reality

  • Official: PurpleAir sells replacement laser counters; Classic Plus variant has updated internal bracket for easier component maintenance (per community forum staff post, snippet-derived).
  • Community-reported support reputation: not directly observed in this pass — UNVERIFIED.

Accuracy (attribution only — never our finding)

  • Manufacturer (PurpleAir community "Research Considerations" page, snippet-derived 2026-09-23): "very precise at estimating PM2.5 and below"; "our PM10 data is not of the same quality, and we do not recommend using it."
  • EPA research (Barkjohn et al. 2019, via Institute for Energy Research summary, snippet-derived): PurpleAir sensors "consistently overpredict fine particle concentrations" vs regulatory monitors; EPA published a US-wide correction equation used for the AirNow Fire and Smoke Map.
  • 2026 Changchun field study (ResearchGate, snippet-derived): IQAir/PurpleAir/AirGradient vs national reference, r=0.92–0.95 across conditions; PurpleAir showed "stable linear correlation yet persistent positive overestimation"; coarse dust degraded all low-cost sensors most severely for PurpleAir.

Buyer questions

  • Which pollutants does it NOT measure? CO2, VOC, radon, temperature, humidity, pressure — PM only.
  • Is the data trustworthy vs reference? PM2.5 is the defensible metric (manufacturer + EPA + independent studies agree, with overprediction bias correctable); PM10 should be ignored per manufacturer. Not regulatory-grade.
  • Subscription/paywall features? PurpleAir map is free to view; API pricing exists per airgradient.com comparison ("Pricing" for API) — details UNVERIFIED in this pass.

Community verdict

The reference point for crowdsourced outdoor PM2.5, with the largest owner map network, but it is a single-pollutant instrument: buyers wanting CO2, VOC, or radon must look elsewhere. PM10 readings should be treated as unreliable by the maker's own admission.

UNVERIFIED / gaps

  • Current 2026-09-23 manufacturer-direct price (not observed; $229 from ~July 2026 review table).
  • Seed-file Facebook group complaint specifics (May/Aug/Sept 2026 posts) — pending security-review-held group posts read.
  • Community-reported support reputation and failure modes beyond seed leads.
  • API pricing details.

Sources (all observed 2026-09-23; labels per QA rule)