Carbon Filter Size Calculator

Calculator

Airflow *

Typical temporary ventilation ranges from hundreds to thousands.

Target EBCT *

Empty bed contact time in seconds, often 0.05–0.30.

Carbon bed depth *

Deeper beds reduce bypass but increase pressure drop.

Carbon bulk density *

Common granular carbon is roughly 25–35 lb/ft³.

Contaminant concentration

Enter mg/m³ for the dominant odor/VOC load.

Target runtime *

Hours between changeouts or service checks.

Adsorption capacity *

Approximate g contaminant per g carbon, often 0.05–0.30.

Safety factor *

Accounts for humidity, mixed vapors, channeling, and uncertainty.

Face shape suggestion

Shape affects geometry only, not media mass.

Rectangle width/height ratio

Used only for rectangular suggestions, like 1.5.

Example data

Scenario	Airflow	EBCT	Bed depth	Concentration	Runtime	Capacity	Safety
Paint odor control in enclosed corridor	1200 CFM	0.15 s	2 in	25 mg/m³	8 h	0.20 g/g	1.25
Waterproofing VOCs during night shift	2000 CFM	0.20 s	3 in	35 mg/m³	10 h	0.15 g/g	1.40
Odor mitigation for temporary negative air	3500 m³/h	0.12 s	60 mm	15 mg/m³	6 h	0.25 g/g	1.20

Examples are illustrative. Validate with site measurements, pressure-drop limits, and media vendor data.

Formula used

Flow conversion: Q (m³/s) = CFM × 0.000471947 or Q = (m³/h) ÷ 3600.
EBCT volume: V_EBCT (m³) = Q × EBCT.
Bed area: A (m²) = V ÷ depth.
Round diameter: D (m) = √(4A/π).
Contaminant load: m (g) = concentration(mg/m³) × Q(m³/s) × runtime(s) ÷ 1000.
Capacity sizing: carbon(kg) = [m(g) ÷ capacity(g/g)] ÷ 1000 × safety.
Selected media: carbon = max(carbon from EBCT, carbon from capacity).

This calculator provides planning-grade sizing for activated carbon beds. For critical applications, verify with breakthrough curves and manufacturer specifications.

How to use this calculator

Measure or estimate airflow through the filter location.
Choose EBCT based on the contaminant type and odor sensitivity.
Set a practical bed depth that fits your housing and pressure limits.
Enter concentration and runtime to capture total contaminant load.
Use a realistic adsorption capacity and add a safety factor.
Press Calculate and review the selected media mass and face area.
Export CSV or PDF for submittals, logs, or procurement notes.

Activated Carbon Role on Construction Sites

Activated carbon filters are widely used during interior fit‑out, waterproofing, painting, and demolition when odors and VOCs must be controlled. Correct sizing helps maintain acceptable air quality while limiting nuisance complaints from adjacent spaces. Oversized beds add cost and can overload portable fans. Undersized beds reach breakthrough early, forcing unplanned changeouts and downtime. This calculator supports fast, documented sizing decisions for temporary or permanent housings.

Inputs That Drive Filter Sizing

Airflow sets the volume of air that must contact the media. EBCT represents the contact time through an empty bed and strongly influences required bed volume. Bed depth converts that volume into face area and drives pressure drop. Bulk density converts volume into media mass for purchasing. Concentration, runtime, and adsorption capacity estimate contaminant loading to check whether the bed will last long enough between service intervals.

Reading EBCT Versus Capacity Outputs

The calculator performs two checks: an EBCT-based media mass and a capacity-based media mass. EBCT ensures adequate contact time for adsorption and is often the governing criterion for odor control. Capacity ensures enough carbon is available to capture the expected contaminant mass over the planned runtime. The recommended size is the larger of the two, then expressed as mass, volume, and face geometry.

Installation Quality and Pressure Limits

Field performance depends on installation quality. Seal bypass points, use uniform screens, and avoid channeling caused by uneven loading. Maintain reasonable face velocity to reduce turbulence and improve contact. Confirm that the fan can overcome the added pressure drop of the carbon bed and any prefilters. In humid environments, capacity can decline and microbial odors may appear; a higher safety factor and more frequent inspections are prudent.

Documentation and Maintenance Planning

Use the exported report to support submittals, procurement, and daily logs. Record measured airflow, operating hours, and odor observations to refine assumptions over time. When replacing media, weigh spent carbon and compare to predicted usage to validate capacity. For multi-zone projects, run separate scenarios for each airflow path and select standardized housing sizes to simplify stocking and maintenance during phased construction schedules more efficiently.

FAQs

1) What EBCT should I start with for odor control?

Many temporary odor applications begin around 0.10–0.20 seconds. Use higher EBCT for difficult VOC mixes, sensitive occupants, or higher humidity. Verify with field odor checks and vendor guidance.

2) Why does the calculator sometimes pick the capacity result?

If concentration and runtime imply a large contaminant mass, the capacity check can exceed EBCT sizing. That indicates the bed may reach breakthrough before the planned service interval unless more media is used.

3) How do I estimate adsorption capacity?

Capacity depends on vapor type, temperature, humidity, and carbon grade. Use manufacturer data when available. For planning, start with conservative values such as 0.05–0.20 g/g and apply a safety factor.

4) What does face velocity tell me?

Face velocity is airflow divided by filter face area. Lower values generally improve contact and reduce turbulence, but increase housing size. Keep velocity consistent across projects to improve repeatability.

5) Does deeper bed always perform better?

Deeper beds can improve contact and reduce bypass risk, but they also increase pressure drop. The best depth balances fan capability, footprint limits, and the level of odor control required.

6) Can I use this for permanent systems?

Yes, as an early sizing tool. For permanent designs, confirm pressure drop, housing details, and breakthrough performance using laboratory curves, manufacturer specifications, and project-specific monitoring plans.