Weld Fume Management: Evaluating Environmental, Source Capture and PPE Solutions and Choosing the Best for Your Application
January 25, 2012
While process changes are the first step in reducing welding fumes, fume extraction and respiratory solutions are critical tools for employee health and safety.
As you talk with different welding operations, each one has a different reason for weld fume management. Some companies have tested their environment and have particulate saturation above and beyond the permissible exposure limits (PEL) deemed acceptable by OSHA. Others simply want to limit the amount of particulate emitted into the environment for employee wellbeing.
The methods each company takes to reduce its weld fume exposure will be different, but there are a number of common factors to take into consideration when selecting a solution. Process and behavioral changes are the prescribed first step, but are not always feasible due to weld requirements and the processes involved. It is then that engineering controls, such as building ventilation and source capture, as well as personal protective equipment (PPE), may need to be implemented. In this article we’ll take a look at the pros and cons of some of these solutions and factors to consider when selecting a solution.
A note: every welding environment is different and needs to be evaluated by a qualified Industrial Hygienist to determine the appropriate course of action for fume controls. This article is presented for awareness and educational purposes only and should not replace professional consultation.
The First Wave of Defense: Work the Process
Before implementing any engineering or mechanical controls, the first step a company must take in weld fume management is changes to the welding process itself. These may include:
- Changing base materials
- Enclosing the process
- Switching wire types (changing from a Flux Cored wire to a solid wire, for instance)
- Change the welding process (from Stick to MIG, for instance)
- Change transfer methods (example: change from short-circuit or globular transfer to Pulsed MIG)
- Change deposition rates and/or weld settings
- Change welder behavior
While not the focus of this article, each of these factors affects change on fume levels but needs to be examined thoroughly in the context of your welding application. Some of these will require testing and certification to ensure welding tolerances are maintained, and in some cases recertification may need to take place. Behavioral change is one of the more immediate changes a welder can make: don’t position yourself directly above the weld (weld fumes rise). When possible, position the weld away from the welder, and never stand in between a fan and the weld — as that fan moves air, it will move weld fume right through the breathing zone of the welder.
Engineered Solutions: Environmental and Source Capture
Once the process has been evaluated, companies will then look at ways of removing the fumes and particulate that result from the welding process. With this, the main goal is to capture the fume.
Environmental solutions, such as industrial HVAC and ventilation systems, may be an option for some but lack the efficiency of source capture through a fume extraction device. These systems are designed to protect the whole shop, which is important when you have other workers in close proximity to the welding activity. These systems, however, are not without inefficiencies. They do not protect the welder’s immediate breathing zone. They can be extremely expensive to implement with changes to the building. While weld fume tends to naturally rise, it eventually levels out and falls back down to the surface — buildings with tall ceilings may prove inefficient at actually removing the particulate.
Source capture through fume extraction is ultimately the best method for eliminating the weld fume from the air. Fume extraction solutions come in multiple shapes and sizes:
- Portable/mobile floor models
- Stationary/wall-mounted models
- Fume guns (welding torch with built-in fume extraction)
- Centralized industrial (multi-cell) systems
Source capture is preferred because it removes contaminated air at the source before it reaches a worker’s breathing zone. One of the key disadvantages of some source capture solutions is that they are difficult to position over large weldments or other obstructions within the weld cell. You also have a number of additional factors to consider:
- Filter ratings: All weld fume extraction equipment filters should have a Minimum Efficiency Reporting Value (MERV). Many filters are not designed to handle the submicron particles (95 percent are .3 to 1 micron) found in welding fumes. Standard cellulose filters rate a 7 to 10 on the MERV scale, which means they are not rated to capture particles smaller than 1 micron. Another common filter material is spun-bound polyester; it is rated an 11 on the MERV scale. An 11 rating indicates that these filters are not very efficient at capturing particles smaller than 1 micron, either. FilTek™ XL filters, with MERV ratings ranging from 13 to 16, offer some of the highest MERV ratings for fume extraction systems. Filters with MERV ratings of 15 and 16 immediately capture up to 95 percent of submicron particles found in welding fumes and quickly begin to filter out up to 99.998 percent of submicron particles.
- Filter media cleaning: You have a number of options to choose from: disposable, manual cleaning, self-cleaning, and automated/online cleaning. Self-cleaning and automated model options are going to cost more upfront, but ultimately have a greater long-term value than models with disposable filters when you factor in the costs of the disposable filters you are continually paying for.
- Airflow: All fume extraction systems are rated based on the amount of cubic feet of air they extract each minute (cubic feet per minute or "CFM"). Each manufacturer ranks CFM differently. CFM should be tested at the hood for the most true/effective rating.
Welding fume extraction systems come in all shapes and sizes. Systems are divided between low-vacuum/high-volume solutions and high-vacuum/low-volume solutions. With low-vacuum/high-volume you are processing a larger volume of air but at generally lower vacuum pressures. Think of the HVAC system in your house, large ducting with high volumes of air. Advantages to these systems include greater capture distances (compared to a high-vacuum system). With high-vacuum/low-volume systems the capture distance is much closer to the weld. High vacuum is typically through a fume extraction gun or a smaller attachment, such as a nozzle. The airflow in these systems are more like a vacuum cleaner. The smaller hoses and ducting helps get into confined spaces and removes the fume much closer to the weld itself. Here are a few examples and considerations:
- Portable: FILTAIR® 130: extremely quiet and extremely portable, this high-vacuum fume extractor features a small footprint on wheels that allows the operator to maneuver into small spaces and hard to reach areas. Ideal for contractors, MRO applications and operations where welding occurs infrequently, the FILTAIR 130 features numerous attachments, a nominal airflow of 132 CFM and is designed for capturing submicron particles found in weld fume.
- Mobile: FILTAIR MWX Series: The self-cleaning model in this high volume series features a FilTek XL surface-loading filter (the weld particulate does not penetrate deep into the filter which makes it easier to pulse clean). Ideal for industrial applications, the MWX Series features an Accu-Rated airflow of 875 CFM at the hood and a MERV 15 rating.
- Stationary/Wall Mounted: FILTAIR SWX Series: Similar to the MWX Series (FilTek XL filters, 875 CFM, MERV 15), a wall-mounted version can be expanded to two arms and takes the footprint off the shop floor—ideal for dedicated weld cells.
- Stationary/Floor: FILTAIR 400 High Vacuum System: Four-port access allows this unit to be centrally located while providing a mobility of nozzle attachment accessories, including a fume gun. Miller’s MERV 16 FilTek XL filter technology (surface loading) captures submicron particles, and the unit features automated filter cleaning for very low maintenance and lower operating costs.
- Fume Extraction Guns: Bernard® FILTAIR Fume Extraction MIG Gun Series (coming soon): Captures the fume right at the torch and connects seamlessly to the FILTAIR 400. Comes in 300- and 400-amp models that feature adjustable extraction control, a smaller vacuum chamber and a 50-degree neck for better joint access.
- Industrial Stationary/Multi-Cell: FILTAIR Industrial Centralized Weld Fume Extraction Series: five models range from 2,000 to 12,000 CFM and can be customized for a wide variety of welding environments and applications; system can also be matched with Miller’s new Automation Hood for PerformArc™ Robotic Welding System cells. Ideal for heavy industrial applications with multiple welding cells, this system combines Miller FilTek XL filter technology with a MERV 15 rating to guarantee superior performance while taking up to 65 percent less floor space than traditional cartridge collectors. CFM varies depending on the size of the unit, with the highest rating reaching 13,440 CFM.
As previously mentioned, there are cases where source capture may not be an optimal solution, such as large weldments where it is not practical or possible to constantly have an extraction hood or attachment right at the weld. Constantly moving hoods and attachments around large, complicated parts may not be physically possible. In applications where companies are not able to get the PEL below acceptable levels with process changes or source capture, then a respiratory solution is required. There are a number of respiratory options for welders, including Powered Air Purifying Respirators (PAPRs), half masks, and supplied air solutions.
To determine the proper respiratory solution, one must calculate the Maximum Use Concentration (MUC). This is done by multiplying the material’s PEL by the Assigned Protection Factor (APF) of the respirator. If the resulting number is higher than the material of concern’s concentration found during testing, then the solution will suffice. For instance, if you test your facility after the other process and engineering controls have been implemented, and you have a hexavalent chromium rating of 65 µg/m3, you will need a device with a MUC that exceeds that. Multiply the PEL of hexavalent chromium (5 µg/m3) by the APF of a PAPR (APF 25) and you get a MUC of 125 µg/m3. This indicates the PAPR will adequately protect the welder in this environment. As we stressed before, it is critical to work through this with a certified industrial hygienist – this article is simply intended to be educational.
Here are a few respiratory options for welders:
- PAPRs: Miller’s PAPR features an APF of 25 and is lightweight with shoulder straps that evenly distribute the weight of the system for optimal comfort. NIOSH certified, Miller has matched the PAPR with its Titanium 9400i auto-darkening welding helmet (with an integrated grinding shield) so that welders can perform all welding and related functions without ever removing the helmet/device.
- Half-masks: Miller will soon be offering an LPR100 Low Profile Respirator P100 Half Mask that features an APF of 10 and fits easily under most welding helmets.
- Atmosphere Supplying Respirators: These systems provide clean air from an uncontaminated source and are often larger and more cumbersome than are necessary in most welding applications. However, with APFs ranging from 1,000 to 10,000, it is an extremely safe option.
One interesting trend we see with PAPRs, in relation to our model with the integrated grinding shield, is that companies are looking at the product as a way to prevent eye injuries. Having the head completely sealed up prevents any outside contaminants from getting into their eyes and causing injuries. While PAPRs are intended for respiratory protection, this is another valuable benefit from the use of the PAPR technology.
Weld fume extraction and employee safety do not have to be complicated endeavors – working with a certified industrial hygienist to determine the best way to manage welding fumes will ensure your employees are working in a healthy environment that they feel good about working in. This will not only ensure that you’re meeting safety requirements, but that you’re also keeping your welders happy and feeling good about coming to work everyday—an important factor in productivity and quality.