# Ventilation & Airflow API > Ventilation and airflow maths as an API, computed locally and deterministically. The air-changes endpoint relates the air changes per hour, the airflow in CFM and the room volume — ACH = CFM × 60 ÷ volume — and solves whichever you leave out (the volume can be given directly or as length × width × height), reporting the airflow in cubic metres per hour too. The required-cfm endpoint applies the ASHRAE 62.1 breathing-zone rule, outdoor airflow = people × Rp + floor area × Ra, with sensible office defaults (5 CFM per person and 0.06 CFM per square foot), to size the fresh-air a space needs. The duct-velocity endpoint computes the air velocity in a round or rectangular duct from the flow and the duct size, V = CFM ÷ area, in feet per minute, metres per second and miles per hour, with guidance on whether it is in the quiet residential or noisier high-velocity range. Everything is computed locally and deterministically, so it is instant and private. Ideal for HVAC, building-services, indoor-air-quality and facilities app developers, ventilation-sizing and duct-design tools, and engineering education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is ventilation and airflow; for heating and cooling load sizing use an HVAC API. ## Authentication All requests require your oanor API key in the `x-oanor-key` header. Get one at https://www.oanor.com/developer/keys. ```bash curl -H "x-oanor-key: oanor_live_…" "https://api.oanor.com/ventilation-api/..." ``` ## Pricing - **Free** (Free) — 2,000 calls/Mo, 2 req/s - **Starter** ($9/Mo) — 30,000 calls/Mo, 5 req/s - **Pro** ($24/Mo) — 150,000 calls/Mo, 15 req/s - **Mega** ($69/Mo) — 750,000 calls/Mo, 40 req/s ## Endpoints ### Ventilation #### `GET /v1/air-changes` — Air changes per hour **Parameters:** - `volume` (query, optional, string) — Room volume (ft³) Example: `1000` - `length` (query, optional, string) — Or length (ft) - `width` (query, optional, string) — Width (ft) - `height` (query, optional, string) — Height (ft) - `cfm` (query, optional, string) — Airflow (CFM) Example: `200` - `ach` (query, optional, string) — Air changes per hour **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/ventilation-api/v1/air-changes?volume=1000&cfm=200" ``` **Response:** ```json { "data": { "ach": 12, "cfm": 200, "note": "ACH = CFM × 60 / volume(ft³). Air changes per hour is how many times the room's air is fully replaced each hour.", "inputs": { "solved_for": "ach", "volume_ft3": 1000 }, "volume_ft3": 1000, "airflow_m3h": 339.8022 }, "meta": { "timestamp": "2026-06-04T18:38:01.952Z", "request_id": "e54036be-e3a1-474f-885d-ef3766764616" }, "status": "ok", "message": "Air changes", "success": true } ``` #### `GET /v1/duct-velocity` — Duct velocity **Parameters:** - `cfm` (query, required, string) — Airflow (CFM) Example: `400` - `diameter` (query, optional, string) — Round duct diameter (in) Example: `10` - `width` (query, optional, string) — Or rectangular width (in) - `height` (query, optional, string) — Rectangular height (in) **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/ventilation-api/v1/duct-velocity?cfm=400&diameter=10" ``` **Response:** ```json { "data": { "note": "Velocity = CFM ÷ duct area. Round area = π(d/2)²; rectangular = w·h. Keep main ducts roughly under 1200–1500 fpm to limit noise.", "inputs": { "cfm": 400, "shape": "round", "duct_area_ft2": 0.545415 }, "guidance": "residential / branch ducts", "velocity_ms": 3.7256, "velocity_fpm": 733.386, "velocity_mph": 8.3339 }, "meta": { "timestamp": "2026-06-04T18:38:02.059Z", "request_id": "ce2a264d-75ed-4e7d-b0c9-992cf75563e3" }, "status": "ok", "message": "Duct velocity", "success": true } ``` #### `GET /v1/required-cfm` — ASHRAE required CFM **Parameters:** - `people` (query, optional, string) — Number of occupants Example: `5` - `area` (query, optional, string) — Floor area (ft²) Example: `500` - `rate_per_person` (query, optional, string) — Rp (CFM/person) Example: `5` - `rate_per_area` (query, optional, string) — Ra (CFM/ft²) Example: `0.06` **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/ventilation-api/v1/required-cfm?people=5&area=500&rate_per_person=5&rate_per_area=0.06" ``` **Response:** ```json { "data": { "note": "ASHRAE 62.1: outdoor airflow = people × Rp + area × Ra. Office defaults Rp = 5 cfm/person, Ra = 0.06 cfm/ft².", "inputs": { "people": 5, "area_ft2": 500, "rate_per_area": 0.06, "rate_per_person": 5 }, "area_cfm": 30, "people_cfm": 25, "required_cfm": 55, "required_m3h": 93.4456 }, "meta": { "timestamp": "2026-06-04T18:38:02.164Z", "request_id": "004ba6b5-7d85-4d32-bc72-72063e8d74ed" }, "status": "ok", "message": "Required CFM", "success": true } ``` ### Meta #### `GET /v1/meta` — Spec **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/ventilation-api/v1/meta" ``` **Response:** ```json { "data": { "notes": "Imperial: volume ft³, airflow CFM, area ft², duct size inches, velocity fpm (also m/s and m³/h). ASHRAE office defaults Rp = 5, Ra = 0.06.", "service": "ventilation-api", "formulae": { "air_changes": "ACH = CFM × 60 / volume(ft³)", "required_cfm": "CFM = people·Rp + area·Ra", "duct_velocity": "V(fpm) = CFM / area(ft²)" }, "endpoints": { "GET /v1/meta": "This document.", "GET /v1/air-changes": "ACH ⇄ CFM ⇄ room volume — supply any two.", "GET /v1/required-cfm": "ASHRAE 62.1 outdoor airflow from people and floor area.", "GET /v1/duct-velocity": "Air velocity in a round or rectangular duct from the flow." }, "description": "Ventilation and airflow calculator: air changes per hour from flow and room volume, ASHRAE required ventilation from occupancy and area, and duct air velocity from flow and duct size." }, "meta": { "timestamp": "2026-06-04T18:38:02.284Z", "request_id": "75c8dd85-20a6-4bd9-b7c5-bb60d10bdb33" }, "status": "ok", "message": "Meta", "success": true } ``` --- Marketplace page: https://www.oanor.com/api/ventilation-api OpenAPI spec: https://www.oanor.com/api/ventilation-api/openapi.json