Two foam ceramics with the same PPI can have different porosity, strut thickness, density, strength and pressure drop. Use PPI to describe pore fineness and porosity to describe void volume, then evaluate both with the actual application.

Foam ceramic PPI indicates pore density, not total porosity. Select PPI by balancing required filtration or catalyst area against pressure drop, fouling risk, coating thickness and mechanical strength.

RTO honeycomb replacement should match more than block dimensions. Review channel count, channel size, wall thickness, open area, surface area, material, weight, strength, thermal properties and previous fouling or cracking history before approving an equivalent.

Clean honeycomb ceramic according to deposit type. Loose dust, organics and inorganic scale require different methods. Avoid uncontrolled high pressure, impact and chemically aggressive cleaners that can damage thin ceramic channels.

Excessive gaps between honeycomb ceramic blocks allow low-resistance gas bypass and reduce effective heat-transfer volume. Installation must control joint and perimeter gaps while still allowing appropriate thermal expansion.