Reading the Rating on a 950 CFM Carbon Filter
This trips people up more than any other spec in a ventilation build. The 950 CFM printed on this filter is the scrubbing rating, meaning air recirculated within the room. Put the same filter inline on an exhaust fan and you halve it, to roughly 475 CFM. Size your fan against that second number. A 6 in or 8 in fan moving 700 CFM will choke against this filter in an exhaust configuration.
Matching an 8 inch Carbon Filter to Your Ducting
The flange is 8 in, so it lands straight on 8 in ducting with no reducer and no adapter. The body runs 43.25 in overall by 12.5 in across, at 53 lbs, which is worth planning a hanger for before it arrives. Inside is RC 412 virgin carbon in a bed roughly 2 in deep, packed rather than pelletized. That distinction matters. Pelletized carbon uses glues and binders that occupy surface area which would otherwise adsorb odor. A conical internal base spreads airflow across the full length rather than letting it short-circuit through the nearest section. The outer aluminum mesh keeps over half its area open, so the filter adds little static pressure of its own. A prefilter comes with it and catches dust before it reaches the carbon. Wash or replace that sleeve on a schedule. A loaded prefilter is the most common reason an 8 inch carbon filter starts choking a fan that used to pull fine.
Key Features
- 950 CFM scrubbing, roughly 475 CFM exhaust: Halve the printed rating for inline exhaust use, then size the fan against that.
- 8 in flange: Mates directly to 8 in ducting with no reducer in the run.
- RC 412 virgin carbon, roughly 2 in bed: Non-pelletized and packed, with no glues or binders taking up adsorption surface.
- 43.25 in long, 12.5 in across, 53 lbs: Plan the hanger and the headroom before it lands on the bench.
- Conical internal base: Spreads airflow the full length instead of letting it short-circuit near the inlet.
- Prefilter included: Catches dust before the carbon. Service it on a schedule or it will choke the fan.
Technical Specifications
| Specification | Value |
|---|---|
| Product | Phat Filter |
| Model | IGSPF398 |
| Length | 39 in (43.25 in overall) |
| Diameter | 8 in nominal, 12.5 in across the body |
| Flange | 8 in |
| Scrubbing Rating | 950 CFM |
| Exhaust Rating | Approx 475 CFM (half the scrubbing figure) |
| Carbon | RC 412 virgin, non-pelletized |
| Carbon Bed | Approx 2 in |
| Weight | 53 lbs |
| Prefilter | Included |
| Base | Internal conical for even airflow |
| Outer Mesh | Aluminum, over half open area |