Canadian Air Filters production floor in Brampton, Ontario

Air Filter Media Pads & Rolls: A Buyer's Guide

10 min read · Filter Types

Air filter media pads and rolls are sheets of loose, unframed filter media – usually polyester (synthetic) or spun fibreglass – that are cut to size and placed in a permanent frame, holding grid or rack to clean the air. Pads arrive pre-cut to a common size, while rolls are bulk lengths that a maintenance team cuts on site. Because there is no disposable cardboard frame, the only thing thrown away at change-out is the media itself.

Media pads and rolls are the workhorse of make-up air units, older rooftop units with built-in filter racks, spray booths, fan coils, and many industrial exhaust and intake systems. They are generally low-efficiency, low-cost pre-filters rather than the final line of defence, so choosing the right media, thickness and holding hardware matters more than the price per square metre.

Quick facts

Typical efficiency Roughly MERV 4–8 for most polyester and tackified media; fibreglass paint-arrestor media is rated by paint capture rather than MERV
Common forms Pre-cut pads (e.g. 20×20, 20×25, 24×24 in.) and bulk rolls in widths such as 20–60 in.
Thickness About 1/2 in. to 2 in.; 1 in. is the most common
Media Polyester/synthetic fibre, spun fibreglass, tackified synthetic, graduated-density blends
Typical applications Make-up air units, older RTUs, fan coils, spray booths, industrial intakes, equipment cabinets
Replacement interval Every 1–3 months in HVAC; much more often in paint booths and dusty plants
Relative cost Lowest cost per square metre of any HVAC filter format
Best paired with A permanent frame or wire holding grid, and a pleated or bag final filter downstream

In this article:

What media pads and rolls are used for

Media pads and rolls exist because many air handlers were never designed for disposable cardboard-frame filters. Older rooftop units, heating and ventilating (H&V) units and make-up air units often have a permanent steel frame or a set of wire grids that hold a flat sheet of media against the airflow. Replacing only the media keeps waste and freight volume down and lets a site stock one roll that fits several sizes of rack.

Typical roles include:

  • Pre-filter ahead of pleated, bag or rigid filters, capturing lint, insects, seeds and coarse dust so that the more expensive final filter lasts longer.
  • Primary filter in equipment where the main goal is protecting coils and fans, such as make-up air units and unit heaters.
  • Intake and exhaust media in automotive and industrial spray booths, where ceiling (intake) media cleans incoming air and floor or wall (exhaust) media catches overspray.
  • Specialty uses such as compressor intakes, electrical cabinet vents, dryer and textile lint screens, and grow-room intakes.

How filter media captures particles

Flat media pads work on the same mechanical principles as any fibrous filter, but because the fibres are relatively coarse and the media is open, the larger-particle mechanisms dominate.

  • Inertial impaction – heavier particles cannot follow the air as it bends around fibres, so they strike a fibre and stick. This is the main mechanism for pollen, lint and sanding dust.
  • Interception – a particle that passes within one radius of a fibre touches it and is held.
  • Straining (sieving) – particles larger than the gaps between fibres are simply blocked, which is why media pads are excellent at stopping insects, leaves and fluff.
  • Diffusion – very small particles drift randomly into fibres. It plays a minor role in open media, which is why pads are not effective on smoke or fine PM2.5.

Many synthetic media are given a tackifier – a thin, non-drying adhesive coating – so that dust that strikes a fibre stays on it instead of bouncing off or shedding downstream. Graduated-density media (open on the air-entering side, denser on the leaving side) spread dust through the depth of the pad, which raises dust-holding capacity before the pressure drop climbs.

Types of media: polyester, fibreglass and tackified

The three media families behave very differently in service. The table summarises how they compare.

Media type Typical efficiency Strengths Watch-outs Common uses
Polyester / synthetic MERV 4–8 depending on weight and thickness Strong, does not shed fibres, easy to cut, tolerates humidity Some light grades load quickly in dusty air HVAC pads and rolls, make-up air, fan coils
Tackified synthetic Similar MERV range, better arrestance of fine dust Holds dust firmly, good dust-holding capacity Tacky to handle; not for every clean-room or food setting RTU racks, dusty commercial and industrial sites
Spun fibreglass MERV 1–4 in HVAC form Very low resistance, high paint-holding capacity in booth grades Fibres can shed if damaged; wear gloves when cutting Paint-arrestor (exhaust) pads, low-cost equipment protection
Graduated-density blends MERV 5–8 Depth loading, longer life Must be installed the right way round Ceiling and intake media, premium pre-filters

Media is usually specified by thickness and by basis weight (mass per area, often quoted in ounces per square yard or grams per square metre). For a given fibre, heavier and thicker media capture more and hold more dust, but they also add resistance. Ask for the manufacturer's rated efficiency, initial resistance and recommended final resistance rather than relying on weight alone.

Efficiency ratings and pressure drop

When a pad is intended for HVAC use, its efficiency can be tested under ASHRAE 52.2 and expressed as a MERV value; in Europe, ISO 16890 would place most of these media in the ISO Coarse group. Spray-booth media are different: exhaust media are tested for how much paint overspray they capture and hold, and intake media for how well they keep dust off a wet finish. Be careful comparing an "arrestance" percentage with a MERV number – arrestance measures capture of coarse synthetic dust by weight and always looks higher than the particle-count efficiency behind MERV.

Pressure drop is where media pads shine. Because the sheet is open and fairly thin, initial resistance is low, which helps older fans that cannot tolerate dense filters. The trade-off is surface area: a flat pad has far less media than a pleated filter of the same face size, so it loads faster. As a rule, change pads when resistance reaches the equipment manufacturer's recommended final pressure drop, or when the leaving face shows visible dust – whichever comes first. A simple differential pressure gauge across the rack turns guesswork into a schedule.

Frames, holding grids and installation

A pad is only as good as the way it is held. Media that sags, folds or has gaps at the edges lets air bypass around it, and unfiltered air carries dust straight to the coil. Good practice:

  • Use a permanent frame with a support grid on the air-leaving side so the media cannot bow downstream under load. Wire holding frames and expanded-metal backers are common.
  • Cut slightly oversize – usually about 1/4 to 1/2 in. larger than the frame opening on each dimension – so the media seals against the frame edges.
  • Respect direction. Graduated-density and tackified media have an air-entering side, often marked by colour or a printed arrow; the more open face goes upstream.
  • Check the rack seals. Missing blank-offs, bent channels and worn gaskets cause more bypass than the media itself.
  • Cut on a clean table with a sharp knife or roll cutter, and wear gloves and eye protection when handling fibreglass.

Where a site would rather not handle loose media, a framed alternative such as a wire panel filter or a standard pleated filter often drops into the same rack with less labour.

Wire panel filter with pleated media held by a wire grid

Applications in Canadian buildings and industry

Make-up air and rooftop units. Plazas, warehouses and restaurants across Canada run make-up air units that pull large volumes of outdoor air in winter. Cottonwood fluff in early summer, road dust in spring and construction dust near new developments can blind a pad quickly, so many maintenance contracts schedule more frequent changes during those periods.

Spray booths and body shops. Automotive refinish and industrial coating booths use ceiling intake media to keep dust off the finish and exhaust media to stop overspray reaching the fan and stack. Your booth manufacturer, insurer and local fire authority set the expectations for exhaust filter type and change frequency, so follow their instructions.

Industrial plants. Pads protect compressor intakes, motor enclosures and process equipment. In plants where dust is combustible or hazardous, loose media is not a substitute for a properly engineered dust collector – see our guide to dust collector and cartridge filters.

Residential. Pads are rarely the best choice for a home furnace. A pleated filter offers far more surface area and better fine-particle capture during the long heating season and wildfire-smoke events.

Mechanic shop interior with exhaust fumes in the air

Maintenance and cost of ownership

Media pads have the lowest purchase cost of any HVAC filter, but the true cost includes labour, disposal and the energy and coil-cleaning consequences of a loaded or bypassing filter. Practical tips:

  • Log the change date and pressure drop on the unit; patterns quickly show which units need monthly attention.
  • Keep one or two roll widths that cover most racks rather than many pre-cut sizes.
  • Inspect support grids and frames at every change – a torn grid lets media blow into the coil.
  • Store rolls flat and dry; crushed media loses loft and efficiency.
  • Dispose of used paint-booth media according to local waste rules for paint-contaminated materials.

For sites that change hundreds of filters a year, it is worth comparing labour minutes per change: a framed pleated or wire panel filter may cost more per unit yet take less time to install, which can lower total cost.

Buying checklist

  • Confirm the rack type: open frame with grid, slide-in channel, or clip-in holding frame.
  • Measure the actual opening, then add the recommended overlap for cut pads.
  • Choose the media family: polyester for general HVAC, tackified for dusty air, fibreglass or graduated media for spray booths as specified by the booth maker.
  • Check rated efficiency (MERV or booth test), initial resistance and recommended final resistance.
  • Decide on pads versus rolls based on how many sizes you maintain and how much cutting labour you want on site.
  • Plan the stage after the pad – a pleated, bag or rigid final filter for occupied spaces.

Browse our media pads and rolls, or contact the bulk orders team for pallet quantities and custom-cut sizes.

Pros and cons

Advantages Limitations
✓ Lowest cost per square metre ✗ Low fine-particle efficiency
✓ Very low initial resistance ✗ Less surface area than pleated filters, so loads faster
✓ Minimal waste – no disposable frame ✗ Bypass risk if cut or seated poorly
✓ One roll can fit many rack sizes ✗ Labour to cut and fit on site
✓ Easy to cut and handle (synthetic grades) ✗ Fibreglass grades can shed fibres if damaged
✓ Excellent at stopping lint, insects and coarse dust ✗ Needs a permanent frame or grid

Shop at Canadian Air Filters

Media pads & rolls · Wire panel filters · Commercial filters · Bulk orders

Made in Brampton, Ontario and shipped across Canada. Need a size you can't find? Request a custom filter or ask about bulk pricing.

Frequently asked questions

What is the difference between filter media pads and rolls?

Pads are pre-cut to a common size and ready to drop into a frame, which saves time on site. Rolls are bulk lengths that you cut yourself, which suits buildings with many different rack sizes and keeps cost per square metre low.

What MERV rating do media pads have?

Most polyester and tackified pads fall roughly in the MERV 4–8 range, depending on thickness and weight. They are mainly coarse-dust and equipment-protection filters; for fine particles, follow them with a pleated or bag filter.

Which side of the media faces the airflow?

On graduated-density and tackified media, the more open, fluffier side faces the incoming air and the denser side faces downstream. Many media are colour-coded or printed with an arrow; if in doubt, ask the supplier before installing.

Can I use a media pad in my home furnace?

It is possible with a permanent frame, but it is rarely the best option. A 1-inch or deeper pleated filter gives much more media area and better fine-particle capture during the heating season and smoke events.

How often should media pads be changed?

In typical commercial HVAC service, every one to three months is common, but dusty sites and spray booths may need weekly or even daily changes. A differential pressure gauge across the rack is the most reliable trigger.

Is tackified media safe for food or clean environments?

Tackifiers are designed to stay on the fibres, but suitability depends on the specific product and your site's standards. Ask for the manufacturer's data sheet and check it against your facility's requirements before use.

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