Weld Fume: Exhaust or Filter?

When it comes to removing the toxic particulate found in weld fume from shop air, there are two options. Option one is to exhaust the contaminated air outside. Option two involves filtering the air before returning it to the facility.

There are many considerations to take into account when choosing between exhaust and filtration systems, including budget, application and available space. For a variety of reasons, filtration systems are most often the recommended course of action. In this blog post, we'll explore a few of the concerns leading many to steer clear of exhaust systems for maintaining indoor air quality.

Negative Pressure Caused by Exhaust Systems

When designing a system to capture and remove weld fume, the goal should be to maintain balance in terms of air pressure, or, better yet, create a slightly positive pressure environment. This is because negative air pressure can wreak serious havoc on indoor air environments. If you've ever tried to enter a building and had trouble opening the door, as if someone was pulling from the opposite side, chances are negative air pressure was to blame.

Negative air pressure is a result of exhausting air out of the building without returning any air back into the system – a problem not encountered in filtration systems that return air to the environment once it's been cleaned. This “pull” affects much more than just doorways. As a matter of fact, negative air pressure will reduce the performance and efficiency of all exhaust systems in the facility.

Negative pressure can pull carbon monoxide from furnace heaters, water heaters and other natural gas heaters back into the plant environment. Additionally, negative air pressure can cause major problems for facilities operating paint booths as the paint particulate will have to move against the opposite force caused by the air system.

Fighting Negative Pressure with Make-Up Air Units

To counter the negative effects of exhaust systems, a common solution is a make-up air unit. These units introduce air from the outside to “make up” what is lost during exhaust. While they can be an effective way to combat negative pressure environments, make-up air units also pose issues to take into consideration.

Since air is being introduced from outside the plant, make-up air units can drastically increase energy costs due to the need to heat or cool plant air on an almost constant basis. This is like trying to heat or cool your house with the windows and doors open – not exactly efficient! The need to heat or cool made-up air is one of the most often overlooked budget considerations when planning an exhaust system. Over the course of an entire year, heating and cooling made-up air can cost as much as $3 to $4 per CFM.

Determining the Right Filtration System for Your Facility

The preferred alternative to exhausting contaminated air from a facility is filtering it and returning the clean air back to the plant environment. With this method, negative air pressure is avoided and the need to condition the air is lessened. You can find out more about filtration systems and the many reasons they're preferred over exhaust systems in the RoboVent webinar Weld Fumes: Exhaust or Filter?

To learn more about weld fumes, how they affect your indoor air quality and what you can do about them, make sure to watch RoboVent's 5-part webinar series on the subject available at robovent.com/category/webinars/.