Dust Collection Frequently Asked Questions

Health Risks: Fine wood dust can cause respiratory illnesses and aggravate existing conditions. Certain types of wood dust may also cause skin irritation. Providing spot dust collection at machinery and using self-contained ceiling suspended units keeps the shop air virtually dust-free, mitigating health risks and preventing potential workmen’s compensation claims.

Quality Defects: High concentrations of sawdust impair a woodworker’s vision, making accurate cuts, measurements, and assemblies difficult. Furthermore, airborne dust can contaminate paint booths, resulting in defective finishes. For machines like planers, a lack of dust collection allows chips to create indentations in the planed material, leading to product defects.

Dual Benefit: Using both spot dust collection directly at machinery (e.g., planers) and self-contained air cleaners (suspended ceiling units) ensures a comprehensive solution. This dual approach keeps the air clean for health and maintains a dust-free environment necessary for precision and quality product finishing.

To get your woodshop dust collection system designed, you’ll need to gather specific information about your shop and equipment, follow key design principles, and use the recommended resources.

Steps for Designing Your System

The following information will help you in designing your complete central woodshop dust collection system:

1. Gather Essential Shop Information

A complete design requires a detailed understanding of your physical space and machinery needs:

• Scaled Layout of Your Shop: Create a drawing that shows the dimensions of your shop space.

• Machinery Locations: Clearly designate the location of each machine.

• Outlet Sizes or Dust Hoods: Note the size (diameter) of the dust port on each machine or the dimensions of the dust hood you intend to use.

• Ceiling Height: Provide the height of your shop ceiling.

• Obstructions: Note the location and size of any obstructions that the ductwork must navigate, such as columns, beams, vents, or lighting fixtures.

2. Plan the Ductwork and Collector

• Main Duct Running: Indicate your preferable route for the main duct (the largest diameter pipe that runs through the shop).

• Dust Collector Location: Choose the preferred location for the dust collector unit itself.

• Type of Dust: Specify the type of dust you will be collecting (e.g., fine wood dust, chips, mixed materials).

• Simultaneous Operation: Designate which machines will run simultaneously in the shop. This is crucial for calculating the required airflow (CFM) and sizing the main duct properly.

Recommended Design Resources

If you require more information or technical guidance while designing your system, these resources are highly recommended:

For Woodshops (DIY Focus):

Woodshop Dust Control book written by Sandor Nagyszalanczy: This resource provides shop-tested solutions to dust control, allowing you to build the right system for your shop without needing complex calculations.

For Larger or Industrial Systems (Technical Reference):

Industrial Ventilation, A Manual of Recommended Practice written by the American Conference of Governmental Industrial Hygienists (ACGIH): This is the definitive reference source you need when designing a larger system or requiring technical, ongoing “how-to” information. The manual contains a wealth of information on designing Dust and Fume Collection systems.

The actual airflow (CFM) your dust collector delivers in a real-world application will be significantly lower than the number advertised by the manufacturer, often being half of the advertised “free air delivery” once the system is installed.

Manufacturers typically quote a “free air delivery” CFM, which is the volume of air moved when no pipe or ductwork is attached.

Why Actual CFM is Lower

When you install ductwork, fittings, and blast gates, you introduce resistance (measured as Static Pressure) to the system.

• Static Pressure (SP): This is the force the fan has to overcome to pull air through all the components (pipes, elbows, flex hose, filter bags, etc.).

• CFM Drop: When resistance (Static Pressure) is put on a collector, its ability to move air (CFM delivery) decreases. The higher the SP in your system, the lower the actual CFM the fan can deliver to your tools.

How to Find Your Actual CFM

Instead of relying on the “free air” number, you must calculate the needs of your entire system first. It is important to first find out your system’s required CFM and RESISTANCE (Static Pressure), and then purchase a collector that can meet those requirements.

A dust collector must be able to overcome the piping resistance and pull the required air volume from the machines you need to operate simultaneously. You can use specialized tools and resources (like fan performance curves or system design manuals) to determine the necessary CFM and SP.

No, your typical plastic pipe system used for conveying dust cannot be adequately grounded. The fundamental issue lies in the material itself and the subsequent buildup of static electricity.

Why Plastic Ducting Cannot Be Adequately Grounded

When dust particles are conveyed through a plastic (PVC) pipe, the constant rubbing against the plastic surface generates static electricity. This can lead to substantial electrical accumulation.

• Discharge Risk: The accumulated charge eventually seeks to discharge, often into the fine dust particles suspended within the pipe. This condition creates a very high risk of a dust explosion.

• Inadequate Grounding: While some attempt to run grounding wires on the exterior or interior of the plastic pipe, this often fails because the plastic material itself is an electrical insulator. You would need to consider both interior and exterior grounding, which is impractical and often ineffective in plastic systems.

Other Issues with Plastic Pipe for Dust Collection

Beyond the grounding and explosion risk, plastic (PVC) piping is not ideal for proper dust collection system design due to limitations in component geometry:

• Fittings Deficiencies: Plastic pipe systems lack the necessary diversity of fittings required to meet complex design needs.

• Poor Airflow Design: Plastic pipe elbows typically have a very short radius, and plastic tee fittings are often improperly designed for efficient dust removal. These design flaws add excessive resistance (static pressure), leading to an inefficient dust collection system and significantly reducing the actual CFM delivered by your collector.

The Recommended Solution

The solution to these issues is a metal piping system (like spiral pipe or clamp-together ductwork):

• Static Safety: With a metal system, you do not have the primary concern of static electricity developing, as the metal acts as a natural conductor when properly grounded to the collector.

• Efficiency: Metal piping systems offer properly designed elbows, fittings, and accessories that have the correct radius and shape for conveying dust, minimizing resistance and maximizing the performance and efficiency of your dust collector.

We use the standardized small-end (male-end) and large-end (female-end) connection method, similar to professional plumbing fittings, to ensure a secure and airtight system.

Components and Connections

• Fittings & Small Couplings: All fittings and small-end couplings (COUP) are male-end to easily slip into the pipe and flex hose (the female-end).

• Pipe-to-Pipe: A small-end coupling (COUP) is used to connect two pipe sections.

• Fitting-to-Fitting: A large-end coupling (COU2) is used when connecting two male-end fittings directly to each other.

Securing the Connection

To complete the connection, follow these two crucial steps:

1. Mechanical Bond: Secure the connection with pop-rivets.

2. Chemical Bond: Apply silicone caulking around the outside of the connection. Wiping the silicone around the joint creates a strong airtight seal, preventing leakage and maximizing your collector’s performance.

If you ever need to change your system, the silicone caulking can be easily cut with a razor blade, allowing for simple removal and reconfiguring of the fittings.

Yes, we offer flexible hose specifically recommended for CNC router and moulder applications, particularly the clear, specialized antistatic urethane hose.

Recommendation: UMW-AS Antistatic Hose

This medium-weight hose is highly encouraged for general CNC router and moulder applications where visibility and safety are key:

• Part Name: UMW-AS (formerly U30-AS)

• Material: Antistatic Ester-Polyurethane (Pre-PUR®), medium weight (30-mil thickness).

• Key Features: Highly abrasion-resistant, microbe-resistant, and flame-retardant.

• Compliance:

  • Flame-Retardant: According to DIN 4102-B1.

  • Antistatic Safety: Permanently anti-static wall with electrical and surface resistance of $<10^9\ \Omega$ (critical for combustible dust safety).

Yes, Air Handling Systems absolutely fabricates custom fittings, including specialized moulder manifolds. Our complete and capable fabrication facility handles these specialized requests daily.

Custom Fabrication Details

• Specific Examples: We regularly manufacture manifolds for Weinig, SCM Group, Stiles Machinery, among many others, as well as similar manifolds required for many larger sanders being manufactured today.

• General Capability: We are highly diverse in the fabrication of custom round pipe and fittings in general, and encourage customers to forward any required drawings.

Requirements for a Custom Manifold Quote

Since manifolds vary based on how the main pipe approaches the machine, we require a detailed drawing to provide a firm quotation. Your sketch must include the following information:

• Detailed sketch of the manifold.

• Precise placement of the tap outlets.

• Specific diameters for all taps and the main body.

Turnaround Time

Our standard turnaround time for manufactured items like manifolds is typically a few days.

Our facility, Air Handling Systems, is physically located in Woodbridge, Connecticut.

We are conveniently situated near both I-95 and the Merritt Parkway, approximately 90 minutes east of New York City. Customers in the New England or Tri-State Area, and beyond, can pick up orders directly from our warehouse.

Shipping and Logistics

We offer flexible and economical shipping services for all orders, domestically and internationally.

Parcel Service (UPS/FedEx)

We can ship many orders directly via UPS, FedEx.

• Spiral Pipe for UPS: To facilitate shipping via parcel service, we fabricate spiral pipe in 5-foot sections. This allows pipe ranging from 3″ to 16″ diameters to be easily shipped by UPS.

• Rush Orders: We can accommodate Next Day, Second Day, or 3-Day Select requests. Simply provide your UPS, or Federal Express account number for processing.

Freight Service (Common Carrier)

Any spiral pipe outside of the 3″ to 16″ diameter range (or larger orders) must be shipped by common carrier (LTL freight).

Service and Expertise

Our Shipping Department is highly experienced and works to ensure your shipment goes by the most economical carrier, utilizing the services of every major shipping carrier that serves Woodbridge. We are knowledgeable about shipping rates and carriers to different parts of the country and the world.

Yes, absolutely! We sell directly to individuals and companies of all sizes, including small shops.

• No Minimum Order: We do not have a minimum order/quantity requirement, so if you only need a few parts for your Air Handling System, we are happy to service your needs.

• Payment: We accept all major credit cards: MasterCard, Visa, Discover, and American Express.

• Ordering: You can easily place your order online, by phone 203-389-9595 or email sales@airhand.com.

• Shipping: We ship stock within 48 hours.

No, we do not sell the dust collector units themselves. Instead, Air Handling Systems specializes in manufacturing high-quality spiral pipe, fittings, and accessories for connecting them.

We serve as the vital link between your woodworking machinery and the dust collection unit. While we focus on the ductwork infrastructure, our knowledgeable sales staff can provide you with a list of trusted dust collector manufacturers and sources to help complete your system.

The primary difference lies in how and when the dust is separated from the air stream.

Two-Stage Dust Collectors (Recommended)

Since most woodworking dust contains both coarse chips and fine particles, a two-stage system is generally recommended for efficiency and equipment longevity. It consists of three parts: a first-stage cyclone separator, a blower, and a second-stage after-filter.

• How it Works: The cyclone is a cone-shaped vessel. As dust-laden air enters, inertia forces particles toward the outer wall. Coarse particles lose momentum and gravity causes them to settle into the container below before reaching the fan. Only the remaining fine dust exits the top to pass through the blower and into the final filter.

• Key Design Fact: The longer the cyclone body and cone, the better the dust separation.

Single-Stage Dust Collectors

In a single-stage unit, the blower draws 100% of the dust-laden air (chips and fine dust) directly through the impeller before sending it to the filtration bag.

• The Risk: Because coarse wood debris hits the blower impeller directly, single-stage units are prone to blower unbalance and damage. Additionally, the filter receives 100% of the waste material, leading to faster clogging and reduced suction.

Yes, locating your dust collector in an enclosure on an outside wall is highly recommended. This setup offers two primary advantages for your workshop:

• Maximized Floor Space: It removes a large footprint machine from your working area, allowing for more machinery or assembly space.

• Noise Reduction: Placing the unit outside in an enclosure significantly reduces the decibel level inside the shop, creating a safer and more comfortable work environment.

Critical Installation Tip: Recirculating Air

If you move the collector outside, you must account for return air to avoid creating negative pressure or losing heated/cooled air.

The Recommended Setup: Cut a filter frame into the common wall between your outdoor enclosure and the shop, ideally near the ceiling. Insert a standard furnace filter (a 20″ x 20″ size is normally adequate).

• Function: This allows the air to re-circulate back into the shop, preventing heat loss.

• Air Quality: The inexpensive furnace filter acts as a final stage, ensuring that the air returning to the shop is cleaner and free of fine dust.

No, a furnace blower is not suitable for a central dust collection system. While it may seem like a cost-effective solution, these fans (technically known as forward curve or “squirrel cage” fans) are designed for HVAC, not material handling.

Why Furnace Blowers Fail for Dust Collection

There are three critical technical reasons why these fans cannot perform this task:

• Insufficient Static Pressure: A central dust collection system typically generates 8″ to 10″ of static pressure (resistance) that the fan must overcome. Furnace blowers are “light duty” and only capable of approximately 1.5″ static pressure. They simply do not have the strength to pull air through the ductwork and filters.

• Inadequate Air Velocity: To keep heavy wood chips and dust suspended in the air stream, you need a transport velocity of roughly 4,000 FPM (feet per minute). HVAC systems are designed to move clean air slowly at only 1,000 FPM. At this low speed, dust will drop out of the air stream and clog your pipes.

• Wrong Blade Design: Squirrel cage fans have curved, lightweight blades that trap debris. They are not designed for impact.

The Correct Solution: Radial Blade Centrifugal Fans

The type of fan required for dust collection is a radial blade centrifugal fan. Unlike furnace blowers, these are designed for high-performance material handling:

• Self-Cleaning Blades: They feature straight blades that prevent material buildup.

• High Pressure: They are engineered to operate at high speeds, generating the required 12″+ water gauge pressure.

• Heavy-Duty Construction: The housings are typically welded and heavy-duty to withstand the impact of wood chips and debris.

No, the two systems rely on completely different principles of physics and are not interchangeable.

To understand why, you must look at the difference between High Velocity (household) and High Volume (industrial) systems:

1. High Velocity Systems (Residential Central Vac)

• • The Physics: These move a low volume of air (e.g., 50–75 CFM) but at a terrific velocity (normally 8,000 FPM) and high pressure.

  • The Design: Designed to lift heavy dirt from carpets through small pipes and hoses (1″ or 2″ diameter).

2. Conventional Dust Collection (Woodworking/Industrial)

• The Physics: These move a massive volume of air (High CFM) at a lower velocity (normally 4,000 FPM).

• The Design: Designed to capture floating dust and chips from machinery through large pipes (4″, 5″, 6″+ diameter).

Summary: The “Milkshake” Analogy

Because the sciences do not overlap, mixing the components results in failure:

• Shop Collector on Home Piping: If you try to pull a conventional dust collector’s volume through a 1½” central vac hose, it is like trying to suck a milkshake through a cocktail straw. The resistance is too high, and airflow stops.

• Shop Vac on Industrial Machine: Conversely, if you attach a 2″ high-velocity vacuum hose to a planer with a 5″ outlet, the vacuum lacks the CFM volume to evacuate the hood, leaving the machine clogged.

No, it is not recommended to attach a general air filter plenum to a single-stage dust collector.

While your unit is rated at 1200 CFM, attempting to use it for general shop ventilation will likely fail for three technical reasons:

1. Insufficient Real-World Volume: The “1200 CFM” rating is likely Free Air Delivery (0″ static pressure). Once you add the resistance of a filter plenum, the actual airflow will drop significantly, leaving you with insufficient suction for both the room and your tools.

2. Wrong Application: Dust collectors are engineered for Source Capture (high velocity/pressure at a specific machine). They are not designed for General Ventilation (high volume/low pressure) to clean the ambient air in a room.

3. Filter Resistance: Adding a 24″ x 24″ filter creates excessive Static Pressure. A single-stage blower simply does not have the performance curve to overcome this resistance and still move air effectively.

The Correct Solutions

1. For Sanding (Source Capture): Instead of trying to filter the whole room, capture the dust at the source. Attach an Air Handling Systems Galvanized Nozzle to a flexible hose connected to your collector. Position the nozzle directly next to your sanding operation to capture the dust before it becomes airborne.

2. For Cleaning Shop Air (Ambient Filtration): To filter floating dust from the shop air, use a dedicated Ambient Air Cleaner (like a ceiling-hung unit). These are specifically designed with the correct fan type to circulate and scrub the air in a room efficiently and inexpensively.

Technical Note: Understanding CFM Ratings

Be cautious with manufacturer CFM ratings. A “1200 CFM” rating usually refers to Free Air—the volume of air moved with no pipe or filters attached.

• The Reality: Every foot of pipe, elbow, and hose you add increases Static Pressure (resistance).

  The Result: As Static Pressure increases, CFM decreases. In a real-world piping system, your actual delivered CFM is often significantly lower than the “Free Air” rating. Always consult the manufacturer’s Fan Performance Curve to see how much air the unit moves at various static pressure levels.

Yes, this is a classic sign of a centrifugal fan spinning in the wrong direction.

It is a common misconception that if a fan spins backwards, it will suck air in through the exhaust. In reality, a centrifugal impeller spinning in reverse will still move air in the correct direction (out the exhaust), but with drastically reduced efficiency and suction power.

How to Check the Impeller Rotation

Since you cannot usually see the impeller itself while it is running, you must check the motor’s cooling fan:

1. The “Bump” Test: Turn the dust collector on and immediately off again.
2. Observe the Motor: While the motor coasts to a stop, look through the grill on the back/end of the motor housing. You will see a disc with cooling fins.
3. Verify Direction: This disc spins in the same direction as the main impeller.

The “Lasso” Visual Test

To determine if that direction is correct, visualize the physics of the fan:

• The impeller must spin in a direction that “throws” the material directly into the outlet chute.

• The Analogy: Think of it like a cowboy whirling and throwing a lasso. The release point must be aligned with the outlet to use the momentum effectively. If it is spinning the opposite way, it is fighting against the housing shape.

Note: Do not assume a standard direction; some blowers are designed for Clockwise (CW) rotation and others for Counter-Clockwise (CCW). Always verify based on the position of the outlet.

Safety Warning: You cannot use the Vacuum Hose Kit with a single-stage collector due to severe fire and damage risks.

The Vacuum Hose Kit is designed for shop floor cleanup, which inevitably involves sucking up heavy wood chips, metal scraps, screws, and nails.

The Dangers of Single-Stage Cleanup

In a single-stage collector, all material passes directly through the fan blower before reaching the filter. Using a floor sweep kit creates two immediate hazards:

1. Catastrophic Impeller Damage: Metal scraps and heavy debris will strike the fan blade (impeller) at high velocity, causing bending, cracking, or shattering.

2. Fire and Explosion Risk: Metal debris hitting a metal fan blade can create sparks. In a dust-laden environment, a single spark can ignite the dust cloud, leading to a fire or explosion.

The Requirement: Two-Stage Systems

The Vacuum Hose Kit REQUIRES a minimum of a 5 HP two-stage collector.

• Why? A two-stage system uses a cyclone or separator to drop heavy chips and metal scrap out of the air stream before they reach the fan. This eliminates the risk of blade damage and spark generation.

Can I get 1-micron filtration for my dust collector?

Yes, you can achieve filtration down to 1 micron. To do this effectively, you need the correct fabric, surface treatment, and the proper Air-to-Cloth Ratio for your application.

• The Recommended Material: For wood dust, we generally recommend Polyester Felt with a Singed Finish.
• The “Dust Cake” Principle: Filtration efficiency actually improves over time. Initially, the felt filters the dust, building up a layer known as a “dust cake” on the singed surface. This cake then performs the actual filtration of subsequent fine dust.
• Self-Cleaning: When the cake becomes too thick, the material naturally wants to clog (blind). However, the singed surface prevents the dust from adhering permanently, allowing the heavy cake to break away and fall into the collection bag, leaving a thin, effective layer behind to continue the process.

Why does my replacement filter bag need to be oversized?

The purpose of an oversized bag is to maintain the proper Air-to-Cloth Ratio (the amount of air passing through every square foot of filter media).

• The OEM Flaw: Most manufacturers of single-stage units include the surface area of the bottom bag in their efficiency calculations.

• The Reality: Once the bottom bag fills with sawdust, that surface area is blocked and can no longer filter air. This drastically reduces your ratio, causing backpressure and suction loss.

• The Solution: An oversized top bag provides enough extra surface area to compensate for the loss of the bottom bag, ensuring consistent suction even as the collector fills up.

What is the difference between OEM standard bags and Polyester Felt?

There is a significant difference in filtration efficiency and airflow between standard factory bags and high-quality aftermarket felt.

• OEM Standard (Polyester Sateen): Most factory-supplied bags are made of woven lightweight polyester sateen. These typically have a poor filtration rating of around 30 microns and offer lower airflow.

• Standard Felt: While better than sateen, standard felt lacks surface treatment, causing dust and woodchips to stick to the fibers.

• Singed Polyester Felt (Recommended): Our recommended bags use a singed surface treatment. This critical step burns off loose fibers, creating a smooth surface that promotes the “dust cake” buildup and release cycle. This allows the bag to essentially “clean itself,” preventing the permanent clogging common with standard OEM bags.