---
title: "Removal efficiency"
description: "Removal efficiency is the fraction of a target pollutant removed by an emissions-control device, parallel to collection efficiency for particulate. Removal efficiency is the standard KPI for gaseous-pollutant control:"
canonical_url: "https://sylio.co/glossary/removal-efficiency"
last_updated: "2026-06-28T02:29:34.807Z"
---

**Removal efficiency** is the fraction of a target pollutant removed by an emissions-control device, parallel to [collection efficiency](/glossary/collection-efficiency) for particulate. Removal efficiency is the standard KPI for gaseous-pollutant control:

<table>
<thead>
  <tr>
    <th>
      Device
    </th>
    
    <th>
      Target
    </th>
    
    <th>
      Typical removal efficiency
    </th>
  </tr>
</thead>

<tbody>
  <tr>
    <td>
      <a href="/glossary/selective-catalytic-reduction">
        SCR
      </a>
    </td>
    
    <td>
      NOx
    </td>
    
    <td>
      80–95%
    </td>
  </tr>
  
  <tr>
    <td>
      <a href="/glossary/selective-non-catalytic-reduction">
        SNCR
      </a>
    </td>
    
    <td>
      NOx
    </td>
    
    <td>
      30–60%
    </td>
  </tr>
  
  <tr>
    <td>
      Wet FGD
    </td>
    
    <td>
      SO₂
    </td>
    
    <td>
      95–98%
    </td>
  </tr>
  
  <tr>
    <td>
      Dry FGD (CFB scrubber)
    </td>
    
    <td>
      SO₂
    </td>
    
    <td>
      85–95%
    </td>
  </tr>
  
  <tr>
    <td>
      Activated carbon injection
    </td>
    
    <td>
      Mercury
    </td>
    
    <td>
      80–95%
    </td>
  </tr>
  
  <tr>
    <td>
      <a href="/glossary/claus-unit-sulphur-recovery-unit">
        Claus unit / SRU
      </a>
    </td>
    
    <td>
      H₂S → S
    </td>
    
    <td>
      95–99.9% (multi-stage)
    </td>
  </tr>
</tbody>
</table>

## How fouling degrades removal efficiency

- **SCR catalyst** — [masking](/glossary/catalyst-masking) and [pluggage](/glossary/catalyst-pluggage) reduce active surface area
- **Wet scrubbers** — internal scaling and spray-distribution problems reduce gas-liquid contact
- **AIG** — fouled [ammonia injection grids](/glossary/ammonia-injection-grid) cause maldistribution

[Sonic horns](/glossary/sonic-horn) on SCR catalyst layers directly defend NOx-reduction efficiency.

## Related terms

- [Collection efficiency](/glossary/collection-efficiency)
- [Selective Catalytic Reduction (SCR)](/glossary/selective-catalytic-reduction)
- [NOx reduction efficiency](/glossary/nox-reduction-efficiency)