# HVAC Air Changes Per Hour (ACH) Calculator

> HVAC Air Changes Per Hour (ACH) Calculator is a paid API for AI agents from hvac-calc.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-30).

Calculates air changes per hour (ACH) from airflow (CFM) and room volume, or computes the CFM needed to achieve a target ACH rate.

## Facts

- Endpoint: GET https://hvac-calc.x402tookit.com/air-changes?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hvac-air-changes-per-hour-ach-calculator-244da913
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_v3gYsthZzSRZlsiXSVLb4

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability hvac-air-changes-per-hour-ach-calculator-244da913
```

Example prompt: What are the air changes per hour for a room that's 20 feet long, 15 feet wide, and 9 feet tall with a fan moving 450 CFM?

## When to prefer this

Choose this endpoint when you need to quickly compute ACH from known airflow and room dimensions, or size airflow for a ventilation target — it is purpose-built for HVAC ventilation rate math and returns structured results with a human-readable summary, making it ideal for automated HVAC compliance checks, design calculations, or educational tools.

## Known failure modes

- Missing both CFM and ACH target — endpoint cannot compute without at least one of these
- Missing room volume and insufficient room dimensions to derive it — requires volumeCubicFeet or all three of lengthFt/widthFt/heightFt
- Non-positive or zero values for dimensions may produce invalid results
- HTTP 402 if payment header is not provided or USDC balance is insufficient

## How this service works

Air changes per hour (ACH) from airflow and room volume, or the CFM needed for a target ACH.

## Output

Returns the computed ACH value (if CFM was provided), or the required CFM (if a target ACH was provided), along with the room volume in cubic feet, minutes per air change, a plain-English summary, and an optional disclaimer. Fields may be null if inputs are insufficient.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [],
     "properties": {
      "ach": {
       "type": "number",
       "description": "Target air changes per hour to get the CFM needed"
      },
      "cfm": {
       "type": "number",
       "description": "Airflow in CFM to get the ACH; send this or ach"
      },
      "widthFt": {
       "type": "number",
       "description": "Room width in feet"
      },
      "heightFt": {
       "type": "number",
       "description": "Room height in feet"
      },
      "lengthFt": {
       "type": "number",
       "description": "Room length in feet"
      },
      "volumeCubicFeet": {
       "type": "number",
       "description": "Room volume in cubic feet; or send lengthFt, widthFt and heightFt"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "ach": {
       "type": [
        "null",
        "number"
       ]
      },
      "cfm": {
       "type": [
        "null",
        "number"
       ]
      },
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "volumeCubicFeet": {
       "type": [
        "null",
        "number"
       ]
      },
      "minutesPerChange": {
       "type"
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/hvac-air-changes-per-hour-ach-calculator-244da913/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from hvac-calc.x402tookit.com](https://www.zero.xyz/host/hvac-calc.x402tookit.com/llms.txt)