---
title: "Filter bag"
description: "A filter bag is the cylindrical fabric sock that traps particulate inside a fabric filter. Bags are typically 120–300 mm in diameter and 2–10 m long, suspended vertically from the tubesheet, supported internally by a wire bag cage and sealed at the top by a snap-band collar."
canonical_url: "https://sylio.co/glossary/filter-bag"
last_updated: "2026-06-28T02:29:24.887Z"
---

A **filter bag** is the cylindrical fabric sock that traps particulate inside a [fabric filter](/glossary/fabric-filter). Bags are typically 120–300 mm in diameter and 2–10 m long, suspended vertically from the [tubesheet](/glossary/tubesheet), supported internally by a wire [bag cage](/glossary/bag-cage) and sealed at the top by a snap-band collar.

## Media selection

Bag media must match the application temperature, gas chemistry, dust load and cleaning system. See [P84 / Nomex / Ryton filter media](/glossary/p84-nomex-ryton-filter-media) and [PTFE membrane filter bag](/glossary/ptfe-membrane-filter-bag).

<table>
<thead>
  <tr>
    <th>
      Material
    </th>
    
    <th>
      Max continuous temp
    </th>
    
    <th>
      Typical use
    </th>
  </tr>
</thead>

<tbody>
  <tr>
    <td>
      Polyester
    </td>
    
    <td>
      135 °C
    </td>
    
    <td>
      Cement, food, light industrial
    </td>
  </tr>
  
  <tr>
    <td>
      Polypropylene
    </td>
    
    <td>
      90 °C
    </td>
    
    <td>
      Wet chemistry, washdown
    </td>
  </tr>
  
  <tr>
    <td>
      Nomex (aramid)
    </td>
    
    <td>
      200 °C
    </td>
    
    <td>
      Asphalt, metallurgical
    </td>
  </tr>
  
  <tr>
    <td>
      P84 (polyimide)
    </td>
    
    <td>
      240 °C
    </td>
    
    <td>
      Cement, biomass
    </td>
  </tr>
  
  <tr>
    <td>
      Ryton (PPS)
    </td>
    
    <td>
      190 °C
    </td>
    
    <td>
      Coal-fired utility, sulphur-rich
    </td>
  </tr>
  
  <tr>
    <td>
      Fibreglass
    </td>
    
    <td>
      260 °C
    </td>
    
    <td>
      Cement, WtE high-temperature
    </td>
  </tr>
  
  <tr>
    <td>
      PTFE (Teflon)
    </td>
    
    <td>
      260 °C
    </td>
    
    <td>
      Aggressive chemistry, sub-mg outlet
    </td>
  </tr>
</tbody>
</table>

## Failure modes

- **Bag blinding** — pore choking that raises ΔP
- **Abrasion** — wear at the bottom of the bag from falling cake
- **Thermal degradation** — exceeding the media's continuous-service rating
- **Hydrolysis / acid attack** — at the cold end below the acid dew point
- **Cage corrosion** — failure of the cage allows bag collapse

## Related terms

- [Fabric filter](/glossary/fabric-filter)
- [Baghouse](/glossary/baghouse)
- [Bag cage](/glossary/bag-cage)
- [PTFE-membrane filter bag](/glossary/ptfe-membrane-filter-bag)
- [Fibreglass filter bag](/glossary/fibreglass-filter-bag)
- [Bag blinding](/glossary/bag-blinding)