• Particle interception depends on both efficiency and resistance.
  Filtration media must be evaluated by both filtration efficiency and pressure drop (airflow resistance). Looking at efficiency alone risks overlooking excessive breathing or ventilation resistance.
• Liquid filtration starts with the medium and temperature.
  Whether the fluid is oil, water, or another chemical medium—and at what working temperature—determines whether the roll can even survive the application.
• Oil absorption relies on sorption, a completely different mechanism from interception.
  Asking for filtration efficiency metrics when sourcing oil-absorbent media won't get you an answer.

Spunbond and Meltblown Are Partners, Not Substitutes
Within the same filter structure, PP spunbond and meltblown serve distinct roles: spunbond provides structural support and outer containment, while meltblown captures fine particles. They work as a composite combination, not replacements for each other. Dust collector bags are a prime example—the outer layer requires strength and sealability, while the inner layer handles filtration and dust holding. Two separate tasks mean two separate material specs.

• Medium & Operating Temperature
  Without defining these, every specification that follows is pure guesswork.
• Efficiency & Pressure Drop (Paired Together)
  These two metrics must be provided as a pair. Giving efficiency alone forces the supplier to guess how much airflow or fluid resistance your system can tolerate.
• Dust-Holding or Absorption Capacity Targets
  In dust collection applications, dust-holding capacity dictates how often bags or cartridges must be replaced—impacting total operating costs far more than initial efficiency.
• Testing Standard
  Specify the exact standard and test method. Writing down a bare efficiency number without a standard leaves buyer and supplier testing by completely different rules at acceptance.

Miss one item, and the "cheaper" quote is simply missing that requirement.
Only when all four items are present can quotes be fairly compared. Whenever one quote looks noticeably cheaper, it is almost always because one of those four parameters was left out.

Lock in the Structure Before Confirming Slitting
Hendar places this engineering evaluation ahead of sampling: define the structure and GSM based on the task first, then finalize slitting widths and roll dimensions. Reversing this order leads to shipping two rounds of samples only to discover the material doesn't match the operating medium.

Write Four Lines Before Placing Your Order
Before sending out your RFQ, write down four lines: medium & temperature, efficiency & pressure drop, dust-holding or absorption target, and testing standard. Sending those four lines upfront eliminates half the back-and-forth.