Why Downdraft Tables are Not Good for Welding Fumes & Three Alternatives

While essential in many industries, welding generates fumes that pose significant health risks. During welding, various toxic gases and fine metal particles are released, which can be hazardous when inhaled. Over the years, multiple methods have been used to manage and control these fumes, with downdraft tables being one. However, are they the best solution for welding fumes? The natural behavior of welding fumes suggests otherwise.

This article seeks to discuss the inefficiencies of downdraft tables for capturing welding fumes and offers an exploration of three alternative methods that can provide a more effective solution.

The Problem with Downdraft Tables for Welding Fumes

Downdraft tables, a popular fume extraction system, operate on a straightforward principle. They draw fumes or dust downward, away from the worker’s breathing zone, and capture them in a filter system within the table. However, this approach presents significant inefficiencies when it comes to welding fumes.

The fundamental problem lies in the natural behavior of welding fumes. When metal is heated during welding, the generated fumes rise upwards due to the heat, following the natural law of convection. The higher the welding power, the faster they move. This upward movement is counter to the downdraft table’s function, which seeks to pull these fumes downward.

Extracting these rising fumes from the bottom can be a Herculean task. It is inefficient and can sometimes prove impossible, particularly in the case of significant volumes of fumes. Instead of helping, the downdraft system often ends up fighting against the natural flow of the fumes, leading to an unnecessary waste of energy and resources.

The airflow required to make a downdraft table work to extract welding fume is much higher than the alternative solutions we will introduce later. A job that a fume extraction gun can do with 100 cfm would require over ten times the airflow with a downdraft table.

Moreover, it’s essential to understand that downdraft tables are ideally suited for specific scenarios, but welding isn’t one of them. They excel at capturing dust from processes such as grinding or cutting, where the particulate matter tends to settle downward. In such instances, downdraft tables efficiently capture and remove these particulates, preventing them from spreading throughout the workspace.

However, for welding fumes, the downdraft approach is like trying to fit a square peg into a round hole. It’s not the best fit, and as we will discuss next, there are alternatives that better align with the natural behavior of welding fumes, providing a more efficient and safer solution.

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Three Alternative Methods for Capturing Welding Fumes

Understanding the limitations of downdraft tables for welding fumes extraction opens the door to exploring better-suited alternatives. Here, we introduce three methods that consider the natural upward movement of welding fumes, thus proving more effective.

Backdraft or Sidedraft Table

Backdraft or side-draft tables offer a slight but important shift in the fume extraction approach. Unlike downdraft tables, they pull the fumes horizontally (side-draft) or backward (backdraft) rather than downwards. While they still face challenges due to the rising nature of welding fumes, their design is slightly more compatible with welding processes. This could be a better choice if a table-based solution is required, although it’s still not the most effective method.

Fume Extraction Arm

A substantial improvement over table-based solutions, the fume extraction arm captures fumes from above directly in their natural movement path. These arms can be adjusted to sit above the welding operation, capturing and extracting the fumes as they rise. This results in more efficient fume control and improved worker protection, making fume extraction arms a significantly better solution than both downdraft and side-draft tables.

Fume Extraction MIG Guns

Arguably the most effective solution for MIG welding is using fume extraction MIG guns. MIG welding, being the most widely used process in the industry, generates a substantial amount of fumes. Fume extraction MIG guns are designed with built-in extraction capabilities, capturing fumes right at the source, which ensures maximum fume extraction and improves visibility for the welder, contributing to more precise work.

Each of these alternatives offers a different approach to handling welding fumes, with varying degrees of effectiveness. The choice depends on several factors, such as the welding process, workspace constraints, and specific safety requirements.

The Limitations of Fume Extraction Hoods

While discussing alternatives, it’s essential to consider the limitations of another popular choice in the industry – fume extraction hoods. These systems work similarly to kitchen exhaust hoods, drawing in fumes from the welding process and directing them away from the workspace. They can be highly effective in specific scenarios, particularly in robotic welding.

However, when it comes to manual welding, fume extraction hoods fall short of providing adequate protection to the welder. The main issue is the position of the welder relative to the weld pool and the extraction hood. In manual welding, the welder’s head often lies between the weld pool and the hood, meaning that the hazardous fumes must pass the welder’s breathing zone before being extracted.

Thus, fume extraction hoods may seem like an ideal solution due to their high extraction rate and suitability for robotic welding, but their effectiveness is significantly compromised during manual welding. It’s crucial to remember that the goal is not just to extract fumes but to ensure that they don’t reach the welder’s breathing zone in the first place.

The Best Fume Extractor for Each Process

Process	MIG gun	Arm	Nozzle	Hood	Table
MIG / GMAW	Best	Yes	Yes	No	No
TIG / GTAW	No	Best	Yes	No	No
Fluxed-Cored / FCAW	Best	Yes	Yes	No	No
Stick / SMAW	No	Best	Yes	No	No
Robotic Welding	Yes	Yes*	No	Best	No
Aluminum Welding	Best**	Yes	Yes	No	No
Grinding***	No	No	No	No	Yes
Plasma Cutting****	No	No	No	No	Yes

Conclusion

Welding fumes pose a significant health risk, and effective control is necessary in any welding environment. Although adequate for specific tasks, downdraft tables are not ideal for welding fumes due to their contradictory nature with the fumes’ upward movement. Alternatives like backdraft or side-draft tables, fume extraction arms, and fume extraction MIG guns offer more suitable solutions, each with unique advantages and considerations.

While fume extraction hoods can be effective in specific scenarios, they do not provide the best protection for manual welding, further emphasizing the need for efficient source-capture methods. Ultimately, the safety and health of welders should be paramount when choosing an extraction method. We can create safer, healthier welding environments by considering the natural behavior of welding fumes and using an appropriate extraction system.

We have two great resources to help you in your effort to manage welding fume. The first is an 8-step method to solve this problem, and the second introduces effective strategies to minimize welding fume.