Baghouse filter fabrics: which one for each temperature

October 21, 2026  ·  Indumor

Choosing a baghouse fabric is a lot like choosing what to wear for welding. A cotton shirt shrugs off a spark; a polyester one melts and sticks to your skin. Filter bags work the same way, except the spark is the gas temperature, and you do not always see it coming. Every fiber has a temperature limit and, on top of that, a chemistry it will not tolerate.

Before: know the gas

Before looking at fabrics you need three facts about the gas: its maximum temperature in continuous operation, its humidity and what it carries — acids, alkalis, oxygen, nitrogen oxides. And you have to tell the operating temperature apart from the peaks: fabric makers quote both, and they are not the same thing.

The continuous temperature is the one that rules. Choosing a fabric by the surge it can take for a few minutes is the fastest way to replace the bags early.

The other fact is the dew point. If the gas or the filter's steel drops below it, water or acid condenses on the cloth and blinds it within minutes or hours. No fiber survives that: the fix is insulating the housing and warming the filter up before dust arrives.

During: what each fiber can take

These are the continuous operating limits recommended by ICAC, the US association of emission control equipment makers, and published by the EPA. Where fiber manufacturers give a different figure, the range is shown:

• Polypropylene: about 93 °C (200 °F), with excellent resistance to acids and alkalis.
• Acrylic homopolymer: 121 to 127 °C (250 to 260 °F). It is used where polyester breaks down in hot, humid gas.
• Polyester: 135 °C (275 °F). It is the workhorse, but it hydrolyzes in hot, moist gas, and its chemical resistance is only fair.
• PPS: 190 °C (375 °F), highly resistant to acids, alkalis and hydrolysis; excess oxygen and nitrogen oxides attack it.
• Meta-aramid: 190 to 204 °C (375 to 400 °F), depending on the source.
• Polyimide: 216 to 246 °C (420 to 475 °F), again depending on the source.
• PTFE: 232 to 260 °C (450 to 500 °F), and practically inert to almost any chemical.
• Fiberglass: 260 °C (500 °F), but it needs gentle cleaning: it does not get along with flexing or rubbing.

Expanded-PTFE membranes deserve a paragraph of their own. Laminated onto the fabric, they filter at the surface: they catch fine dust better and release the cake more easily. But they do not raise the temperature limit, which is still set by the fabric underneath.

After: look after the fabric you chose

A well-chosen fabric is ruined just the same if the filter starts up cold and damp, if a spark reaches the bags or if the differential pressure climbs and nobody looks. That is why, besides the fabric, preheating at start-up, a pre-separator when there are sparks and a differential pressure gauge in plain sight all matter.

If you are working out a whole filter, the guide to sizing a baghouse has the rest of the math; if you are still unsure about the equipment, cyclone or baghouse compares the two; and the history of dust collection tells how industry went from hand-shaken cotton to these fibers. At Indumor we build baghouses and help you choose the fabric with these facts.

Next time you order filter bags, bring three facts in writing: the gas's continuous temperature, its humidity and the chemistry it carries. With those three numbers, the fabric all but chooses itself.

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