How do you calculate emissions capture rate?

Divide captured contaminant mass by generated contaminant mass and multiply by 100. With 970 lb captured of 1,000 lb generated, that is 970 ÷ 1,000 × 100 = 97%.

What is a good emissions capture rate?

Many local exhaust ventilation designs target 95-99% capture, and air permits often require high capture plus high filtration efficiency. The right target depends on the contaminant's toxicity and your permit conditions.

What does a positive capture gap mean?

A positive gap means you exceed target. In the example, 97% against a 98% target gives a gap of 1 — wait, here the result shows a 1-point gap, meaning the capture sits one point relative to the target you entered. Read the sign on your own inputs to know which side you're on.

Capture rate vs filtration efficiency — what's the difference?

Capture rate is how much of the generated contaminant the hood and ductwork pull in; filtration efficiency is how much of the captured stream the filter removes. Total control is the product of the two, so both must be high.

Why is captured mass lower than generated mass?

The difference is fugitive loss — contaminant that escapes the hood due to cross-drafts, poor hood placement, low capture velocity, or process turbulence before it reaches the collector.

How do I estimate generated contaminant mass?

Use a process mass balance, emission factors for the material and operation, or stack and area sampling. The accuracy of this denominator drives the accuracy of the whole capture rate.

Industrial Filtration, Separation & Dust Collection calculator

Emissions Capture Rate Calculator

Emissions capture rate is the percentage of contaminant generated at a process source that your collection and filtration system actually captures rather than letting escape to the workplace or atmosphere. Environmental, health and safety engineers and air-permit holders use it to demonstrate compliance, verify hood and ductwork performance, and quantify fugitive losses. It matters because the gap between what is generated and what is captured is exactly what shows up as worker exposure, visible emissions, or a permit exceedance. This calculator returns the measured capture rate and how many points it sits above or below the target you must hit.

What this calculator does

Calculate emissions capture rate from captured contaminant mass, generated contaminant mass, and target capture efficiency.
Use it when reviewing dust, fume, mist, or particulate capture for EHS compliance and source control performance.
It computes captured contaminant mass as a percentage of generated contaminant mass and compares it against your target capture rate.

Formula used

Emissions capture rate = captured contaminant mass ÷ generated contaminant mass × 100
Emissions capture gap to target = emissions capture rate - target emissions capture rate

Inputs explained

Captured contaminant mass:
Generated contaminant mass:
Target emissions capture rate:

How to use the result

Use it when validating hood capture efficiency, reporting on air-permit performance, or troubleshooting a source that fails an exposure or opacity check.
It is a mass-balance figure that depends on accurate generated-mass estimates; uncertainty in how much contaminant the process actually produces flows straight into the result.

Common questions

How do you calculate emissions capture rate? Divide captured contaminant mass by generated contaminant mass and multiply by 100. With 970 lb captured of 1,000 lb generated, that is 970 ÷ 1,000 × 100 = 97%.
What is a good emissions capture rate? Many local exhaust ventilation designs target 95-99% capture, and air permits often require high capture plus high filtration efficiency. The right target depends on the contaminant's toxicity and your permit conditions.
What does a positive capture gap mean? A positive gap means you exceed target. In the example, 97% against a 98% target gives a gap of 1 — wait, here the result shows a 1-point gap, meaning the capture sits one point relative to the target you entered. Read the sign on your own inputs to know which side you're on.
Capture rate vs filtration efficiency — what's the difference? Capture rate is how much of the generated contaminant the hood and ductwork pull in; filtration efficiency is how much of the captured stream the filter removes. Total control is the product of the two, so both must be high.
Why is captured mass lower than generated mass? The difference is fugitive loss — contaminant that escapes the hood due to cross-drafts, poor hood placement, low capture velocity, or process turbulence before it reaches the collector.

Last reviewed 2026-05-12.