Breathe Better. Live Smarter.®

Measurement evidence behind Terrestream.

One sensor. Twelve signals. Indoor readings connected to outdoor context and plain-English recommendations, backed by a premium measurement stack: Sensirion SEN66 at the core, Bosch BMP390L for pressure context, and Texas Instruments OPT3001 for visible-light context.

Built around components with vendor-published specifications relevant to standards-aligned IAQ monitoring workflows. Sensor selection alone does not confer certification or code compliance.

Contact commercial Download datasheet Compliance path

SEN66 BMP390L OPT3001 Primary-source indexed
Product architecture Measured signals become operational interpretation.

Measured. Indexed. Documented.

Evidence for the signals behind Terrestream.

Terrestream separates sensor capability, field interpretation, standards workflow relevance, and certification boundaries. The measurement stack is source-linked to Sensirion SEN66, Bosch BMP390L, Texas Instruments OPT3001, and Terrestream-owned device documentation.

  • CO₂measured
  • IAQderived
  • VOC Indexindexed
  • NOₓ Indexindexed
  • PM1measured
  • PM2.5measured
  • PM4measured
  • PM10measured
  • Temperaturemeasured
  • Humiditymeasured
  • Pressurecontext
  • Lightcontext

Designed to support standards-aligned monitoring workflows. Certification, code compliance, and project acceptance remain separate professional requirements.

Source-linked stack

Sensirion SEN66, Bosch BMP390L, Texas Instruments OPT3001, and Terrestream device documentation anchor the measurement claims.

Standards-aware path

RESET, WELL, Title 24, and similar workflows require more than sensor selection: installation, calibration, reporting, and governance still matter.

Signal taxonomy

A stack built to explain buildings, not just display numbers.

The page separates direct measurements, Sensirion index outputs, contextual evidence, and Terrestream-derived interpretation so buyers can see exactly where each claim starts and ends.

Measured directly

The primary air-quality channels come from the SEN66 module and are reported as digital outputs.

  • PM1
  • PM2.5
  • PM4
  • PM10
  • CO2
  • Temperature
  • Relative humidity

Indexed

Gas events are reported as Sensirion index signals. They are useful for relative change, not compound identification.

  • VOC Index
  • NOx Index

Contextual

BMP390L pressure and OPT3001 visible-light context help interpret placement, weather, occupancy, and display behavior.

  • Barometric pressure
  • Lux

Derived by Terrestream

Terrestream turns measured and contextual signals into operational interpretation.

  • Source likelihood
  • Recommendations
  • Fleet patterns
  • Maintenance priority

Scenario evidence console

Switch the building story, and the evidence changes with it.

The scenario rail updates CO2, VOC / NOx, and pressure charts so the same stack can be reviewed as a ventilation, combustion, filtration, infiltration, fleet, or compliance workflow.

01

Meeting-room ventilation

CO2 buildup and decay show whether the room recovers after occupancy or needs schedule, damper, or use-pattern changes.

02

Cooking and combustion separation

PM, VOC Index, and NOx Index move differently, giving facilities teams a more useful event fingerprint than a single consumer AQI number.

03

Filtration recovery

PM recovery curves help compare filters, purifier placement, and room-to-room behavior after a particle event.

04

Outdoor pressure context

Pressure movement and outdoor context help explain why a room is importing particles or gases even when the source is outside.

05

Fleet health and maintenance

Repeated source patterns, stuck baselines, and placement outliers become visible when rooms are compared over time.

06

Compliance documentation workflow

Component evidence, source links, conversion assumptions, export cadence, and governance are kept together for project teams.

Core node

One premium node, ten Terrestream outputs.

SEN66 is the primary environmental node. It combines particulate matter, CO2, relative humidity, temperature, VOC Index, and NOx Index in a compact digital module; Terrestream then derives IAQ interpretation from that measured and indexed signal stack.

VOC Index and NOx Index are index outputs, not laboratory TVOC or regulatory NO2 measurements. SEN66 product page

10

Terrestream outputs

Nine SEN66 channels plus Terrestream IAQ interpretation from the measured and indexed signal stack.

source
0-40,000 ppm

CO2 output range

Capability range from the SEN6x datasheet; deployment accuracy depends on configuration and calibration conditions.

source
0-1,000 ug/m3

PM mass range

Datasheet mass-concentration capability for PM channels.

source
0-500

VOC / NOx Index

Index outputs for relative gas events, not laboratory TVOC or regulatory NO2 concentration.

source

Accuracy is not a slogan

Precision, limits, and particle physics stay visible.

Optical PM sensing estimates mass from scattered light. That is practical and powerful, but aerosol density, refractive index, shape, humidity, and coarse-particle statistics still matter.

PM size cascade

datasheet capability

PM1, PM2.5, PM4, and PM10 are size-bucketed mass concentration outputs, not direct chemical identification. SEN6x datasheet

PM SPC precision check

datasheet capability

control band = mean +/- k*sigmaSPC framing makes repeatability visible: the mean, warning band, and control limits stay separate from field accuracy claims.

Sensirion's specification statement distinguishes calibration precision from accuracy and explains why aerosol-specific correction may be needed outside the calibration envelope. specification statement

VOC / NOx index fingerprint

illustrative building scenario

Scenario values are illustrative. Labels remain VOC Index and NOx Index because the sensor does not identify individual gases. SEN6x datasheet

CO2 ventilation decay

illustrative building scenario

C(t) = Cout + (C0 - Cout)e-ACH*tVentilation recovery is evaluated by curve shape and decay rate, not only by a single peak ppm value.

The scenario is illustrative; the hardware capability is sourced to the SEN66 CO2 output range and accuracy notes. CO2 source

Science math

The formulas stay close to the claims.

Professional buyers should be able to inspect how a specification becomes an operating interpretation. These examples keep the vendor formula, sample arithmetic, and limitation note together.

Particle-count penalty

Sensirion source figure

Nrelative = (10 / d)3At equal mass, smaller particles appear far more often in the optical sample volume than coarse particles.

Same mass does not mean same count. Coarse particles are statistically rarer in the optical sample volume. Sensirion statement

PM precision check

Mean plus/minus 2 sigma is the acceptance frame.

typical deviation = μ ± 2σ

At μ = 250 ug/m3, a +/-10% high-range envelope means the typical deviation band should fit inside 225-275 ug/m3.

source

Aerosol statistics

Particle count changes with diameter cubed.

relative count ∝ mass / diameter3

At the same mass concentration, 10 um particles are about 1,000x fewer than 1 um particles, which is why coarse-particle precision is harder.

source

OPT3001 lux decode

The digital register resolves to lux through exponent and result.

lux = 0.01 × 2E × R

Example: E = 8 and R = 250 gives 0.01 x 256 x 250 = 640 lux.

source

Ventilation decay

Recovery is exponential, so slope matters.

C(t) = Cout + (C0 - Cout)e-ACH·t

Illustrative model: 1,400 ppm decaying toward 420 ppm at 3 ACH for 20 minutes lands near 781 ppm.

illustrative scenario source

RESET / WELL VOC pathway

Sensirion publishes the conversion math. We show the boundary.

VOC Index remains the default Terrestream field signal. For building-standard workflows, Sensirion describes a controlled-laboratory pathway for converting VOC Index into TVOC equivalents used by RESET Air and WELL.

VOC Index to TVOC equivalents

vendor formula recreation

Sensirion states the VOC Index to TVOC procedure is valid under laboratory conditions and recommends building-standard tuning parameters, including a 720 h normal learning time offset. Sensirion VOC standards note

Step 1

VOC Index to ethanol equivalent

TVOCethanol=(ln(501 - VOCIndex) - 6.24)×-381.97

Step 2

WELL Mølhave equivalent

TVOCMølhave=(ln(501 - VOCIndex) - 6.24)×-996.94

Step 3

RESET isobutylene equivalent

TVOCisobutylene=(ln(501 - VOCIndex) - 6.24)×-878.53

Boundary

Designed to support standards-aware workflows

Project certification still requires accepted installation, reporting, calibration governance, and the relevant accrediting or project-review process.

WELL accuracy envelope

Sensirion standards note

Sensirion describes WELL's continuously monitoring sensor accuracy envelope as +/-20 ug/m3 plus 15% of measured value and reports its VOC-sensor behavior inside that envelope in the note. accuracy source

Index outputs are still indexes

limitation note
  • VOC IndexRelative gas-event signal and trend output. Use TVOC only inside the Sensirion conversion workflow.
  • NOx IndexCombustion and oxidizing-gas context. It is not a regulatory NO2 concentration analyzer.
  • TVOC pathwayUseful for standards-aligned workflows when assumptions, tuning, and governance are documented.

VOC Index note NOx Index note

Context evidence

BMP390L and OPT3001 explain conditions around the air reading.

Bosch BMP390L

pressure context

Pressure helps with weather, infiltration, HVAC, and placement diagnostics. It is explicitly not an IAQ compliance sensor. Bosch lists 300-1250 hPa operation, typical absolute pressure accuracy of +/-0.50 hPa, and typical relative pressure accuracy of +/-0.03 hPa. Bosch source

Texas Instruments OPT3001

visible-light context

lux = 0.01 x 2E x RThe OPT3001 register format uses exponent and result fields to cover dim rooms and bright daylight without manual range switching.

Lux helps with visible-light environment and display adaptation. It is not circadian or WELL lighting proof. TI specifies 0.01 lux to 83k lux measurements, automatic full-scale ranging, photopic response matching, and typical IR rejection greater than 99%. TI source

Path to compliance use

A clear path from Terrestream readings to a project evidence package.

Terrestream can help project teams gather, interpret, and export data. Compliance still depends on the selected program, monitor acceptance, installation, data governance, and the professional team responsible for submission.

Device regulatory status: FCC Part 15 Class B compliant via Supplier’s Declaration of Conformity; testing by E3C. Read regulatory disclosures.

Component source Measurement class Conversion assumption Export cadence Project governance
01

Select program

Choose RESET, WELL, Title 24, or an internal IAQ policy and document the actual requirement.

02

Map parameters

Confirm PM2.5, TVOC, CO2, temperature, RH, and any project-specific signals that require external measurement.

03

Configure workflow

Set cadence, placement plan, source links, calibration posture, and any Sensirion VOC conversion assumptions.

04

Export evidence

Provide CSV/API/PDF evidence packets to the project team, consultant, BMS, or certification workflow.

05

Govern over time

Maintain placement, calibration, reporting, and project governance outside the sensor alone.

How Terrestream signals map to standards-aligned monitoring workflows.
Signal / requirementTerrestream pathRESET relevanceWELL relevanceStill required outside the sensor
PM2.5 Native SEN66 PM output Core RESET parameter Relevant WELL air-quality parameter Placement, averaging, and program governance
TVOC VOC Index plus Sensirion conversion workflow Requires TVOC concentration workflow WELL Mølhave conversion pathway in Sensirion note Conversion assumptions and project acceptance
CO2 Native SEN66 CO2 output Core RESET parameter Monitoring/ventilation workflow ASC/FRC conditions and project requirements
Temperature Native SEN66 temperature output Core RESET parameter Monitoring/comfort context Placement and comfort-program interpretation
Relative humidity Native SEN66 RH output Core RESET parameter Monitoring/comfort context Calibration governance
NOx / NO2 NOx Index only Event context, not RESET TVOC Not regulatory NO2 measurement External NO2 analyzer if required
Pressure BMP390L context Diagnostic context Not a WELL lighting/IAQ proof point Weather/HVAC interpretation
Lux OPT3001 context Not an IAQ parameter Not circadian/WELL lighting proof Separate lighting compliance workflow
Data platform Dashboard/API/export architecture Can support data transfer workflow Can support feedback/reporting workflow Submission, accreditation, and governance

API export

Structured readings, source classes, and evidence labels for custom compliance dashboards.

MQTT / local workflow

Facilities teams can route signals into local automation or BMS-adjacent systems where appropriate.

CSV evidence packet

Project teams can review timestamped measurements, classifications, and source assumptions.

PDF review packet

Commercial handoff can include component sources, limitations, and standards-path notes.

Consultant handoff

Data is framed for the professionals responsible for installation, reporting, and certification.

Designed for alignment

Standards alignment requires more than components.

Designed to be aligned with standards-aware IAQ monitoring workflows while keeping project certification, installation, calibration, reporting, and governance as separate professional responsibilities.

Limitation note. Sensor selection alone does not confer certification or code compliance. Installation, calibration, reporting, project requirements, monitor accreditation, and governance remain separate requirements. legal accreditation reference
01 Components

SEN66, BMP390L, and OPT3001 provide traceable technical evidence.

02 Workflow

Signal classes, conversion assumptions, and exports stay explicit.

03 Project review

Accreditation, installation, reporting, and submission remain governed.

Signal / requirementWhat the stack providesWhat it can supportRequired outside the sensor
PM Measured by SEN66 Supports monitoring workflows Placement, reporting, and program requirements remain external
CO2 Measured by SEN66 Relevant to ventilation workflows Certification and code compliance require project-specific review
VOC VOC Index; limited lab-equivalent pathways exist in Sensirion notes Useful for trends and events Not a general laboratory TVOC claim in the field
NOx NOx Index Useful for combustion-event separation Not a regulatory NO2 analyzer
RH / T Measured by SEN66 Supports comfort and IAQ context Calibration governance remains a deployment requirement
Pressure BMP390L context Weather, infiltration, and HVAC diagnostics Not an IAQ compliance parameter
Lux OPT3001 context Display and visible-light context Not circadian or WELL lighting proof
Reporting Terrestream dashboard/API architecture Can support exports and facilities workflows Program submissions and governance are outside the sensor alone

Read accreditation status Read sensor compliance index

Manufacturer science

Component-maker science, carried into the product story.

Sensirion, Bosch, and Texas Instruments publish serious technical collateral. Terrestream uses those primary sources to distinguish sensor capability, contextual interpretation, and compliance workflow boundaries.

Sensirion

Gas index plus building-standard conversion

VOC Index and NOx Index remain index outputs, but Sensirion publishes a controlled-lab pathway for VOC Index to TVOC equivalents used in RESET and WELL workflows.

Sensirion

Optical PM precision and aerosol limits

SEN6x PM mass output is calibrated against reference aerosol, while coarse particles and aerosol-specific optical properties still require careful interpretation.

Bosch

Pressure as a diagnostic context channel

BMP390L pressure helps explain weather fronts, infiltration, HVAC pressure behavior, and placement anomalies without pretending to be an IAQ compliance parameter.

Texas Instruments

Human-eye lux response and IR rejection

OPT3001 adds visible-light context with photopic-response matching, automatic ranging, and strong IR rejection, while lighting compliance remains a separate workflow.

From readings to building decisions

A commercial stack for fewer blind spots.

The point is not a brighter consumer display. The point is a defensible telemetry layer that facilities teams can use to explain root cause, tune operations, and prioritize maintenance.

Ventilation

Meeting-room CO2

See buildup and ventilation decay so facilities teams can tune schedules, damper logic, or room-use guidance.

CO2 + decay
Source ID

Cooking and combustion separation

Correlate PM, VOC Index, and NOx Index instead of treating every spike as the same event.

PM + VOC + NOx
Recovery

Filtration recovery

Watch PM recovery time after an event and compare rooms, filters, and purifier placement.

PM slope
Envelope

Infiltration context

Use pressure and outdoor conditions to explain why outside air is helping, hurting, or simply not moving.

Pressure + weather
Portfolio

Fleet maintenance

Surface stuck baselines, placement problems, and rooms that keep producing the same source pattern.

Outliers + baselines

Outdoor context, sourced

Quality indoor data deserves quality outdoor data.

Most monitors stop at the number on the wall. Terrestream sets your indoor measurements against live outdoor weather, air quality, pollen, and wildfire smoke, and we name every source the same way we name every component.

External environmental datastreams fused into the Terrestream experience.
DatastreamProviderWhat it addsRefresh / resolution
Weather Open-Meteo Temperature, humidity, wind, pressure, precipitation, and cloud cover give the outdoor baseline your indoor readings are set against. ≈10 min · 0.5° grid
Outdoor air quality Google Air Quality (US EPA AQI) Outdoor AQI, PM2.5 / PM10, and ozone, plus a 12-hour AQI trend, so indoor-vs-outdoor is a real comparison. ≈30 min · ≈11 km grid
Pollen Google Pollen Tree, grass, and weed pollen index and in-season status (US & Canada). ≈6 h · ≈25 km grid
Wildfire smoke NOAA HMS · NASA FIRMS Smoke-plume and active-fire context, so an outdoor spike is explained rather than guessed. Daily · satellite pass
Climate normals Open-Meteo Archive Historical baselines so “today” is framed against what is normal for your location and season. Reference dataset
Science context NASA (JPL · Earth Observatory) Environmental and natural-hazard briefings surfaced alongside your data. Per source feed
Premium sources, always current. Terrestream draws on premium, commercial-grade data feeds and keeps them continuously refreshed, so your indoor readings are always matched against the latest, highest-quality outdoor information available.

Source library

Primary-source indexed evidence.

Manufacturer pages remain authoritative for third-party component documents.

Primary manufacturer and Terrestream source library.
Document Vendor Date / version Local copy Vendor URL
Terrestream Indoor Air Quality Sensor - Product Datasheet Aerodyne Inc. TSR50035DAI, May 2026 local source
SEN66 product page Sensirion AG Captured 2026-06-01 n/a source
Datasheet SEN6x Sensirion AG 12/2025 local source
SEN6x Sensor Specification Statement Sensirion AG 01/2026 local source
Calibration Certificate SEN5x/SEN6x Sensirion AG Captured 2026-06-01 local source
Compliance of Sensirion's VOC Sensors with Building Standards Sensirion AG Version 1.1, September 2023 local source
Sensirion's VOC Index for Indoor Air Applications Sensirion AG January 2022 local source
Sensirion's NOx Index for Indoor Air Applications Sensirion AG January 2022 local source
BMP390 / BMP390L Datasheet Bosch Sensortec Rev. 002 local copy local source
BMP390 product page Bosch Sensortec Captured 2026-06-01 n/a source
OPT3001 Ambient Light Sensor Datasheet Texas Instruments Rev. C, November 2017 local source
OPT3001 product page Texas Instruments Captured 2026-06-01 n/a source
Sensor Compliance & Documentation Index Aerodyne Inc. 2026-06-01 local source
Accreditation, Calibration, and Building-Standard Statements Aerodyne Inc. 2026-06-01 local source

Breathe Better. Live Smarter.

Deployable building telemetry starts with traceable measurement.

One sensor. Twelve signals. Indoor readings connected to outdoor context and plain-English recommendations, with direct measurements, index outputs, context channels, and operational interpretation kept visibly separated.

$249 USD one-time

Order yours
Setup Datasheet Compliance
  • No subscription required
  • 30-day returns
  • 1-year limited warranty
  • Fast shipping via FedEx

Six sensors. Twelve signals.

Built on genuine Sensirion, Bosch, and Texas Instruments sensors.

  • CO₂
  • IAQ
  • VOC
  • NOₓ
  • PM1
  • PM2.5
  • PM4
  • PM10
  • Temperature
  • Humidity
  • Pressure
  • Light

Included

  • In the box: the sensor, USB-C cable, power adapter, and printed field guide
  • Dashboard and mobile app included
  • Privacy-first air data

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