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When fumes get out of control

What to do when fume extraction equipment fails

This weld shop uses a recirculating system that recycles clean air through the workplace downstream of the fume extraction process. It has been independently tested to produce emissions far below OSHA PELs for the metals contained in welding fumes. (Photos courtesy of Camfil Air Pollution Control (APC), Jonesboro, Ark.)

Minimizing welding fumes in the shop is essential for protecting people, property, and productivity. Learning to read the signs or indicators that your weld fume extraction equipment is not working properly is an essential way to protect your shop environment and the people in it from the detrimental effects of welding fume and particulate.

Signs Your Fume Extraction Equipment Has Malfunctioned

Assuming you have some type of collection or extraction system in place to capture weld fumes, one or more of the following conditions will signal that this equipment is not doing an adequate job.

Excess Buildup of Fumes. It’s inevitable that you’ll find the presence of welding fume within your facility, regardless of the state of your fume extraction system. However, when a system is functioning properly, you should see only fairly light fumes throughout the duration of the shift. For example, in an ambient system that filters all the air in the shop, a light cloud may be visible during working hours but should dissipate during break times or lunch when work ceases. If you notice that the cloud thickens throughout the day, then you probably have a problem.

This doesn’t always mean that your fume extraction system is in disrepair. It may be that your operations have outgrown the fume extraction system because of increased production, or that it was improperly sized at the original time of installation.

Worker Complaints. Welders complaining of health problems or general discomfort are probably being exposed to excessive fumes. Weld fumes are linked to a startling array of both short- and long-term health problems. You should always take complaints very seriously and address them as promptly as possible.

Failure to Pass an Emissions Test. Emissions testing using air sampling techniques is often performed to ensure that a shop is in compliance with OSHA regulations. OSHA has established permissible exposure limits (PELs) based on eight-hour time-weighted averages for hundreds of dusts, including the numerous metals contained in welding fumes.

For further information, a good starting point is the OSHA Fact Sheet, “Controlling Hazardous Fume and Gases during Welding.” By the time a shop fails an emissions test, heavy fume clouds and worker complaints will already be in evidence.

Premature Plugging of Filters and Related Equipment Issues. If the filters in your fume extraction system are failing prematurely and requiring frequent changeout, the culprit may be excessive airflow for the filter media area. The collector may be too small for the job, or the filter pulse-cleaning system may not be working properly. The diaphragm and solenoid valves that regulate pulsing are critical for proper cleaning to occur.

The compressed air system is another potential problem area. If the compressed air pressure is too low, the pulse cleaning system will not clean the filters properly. If the compressed air moisture content is too high, the filter may plug or you could run into solenoid and diaphragm valve difficulties. Moisture problems in compressed air systems are especially prevalent in cold winter months.

The Damaging Effects of Malfunctioning Equipment

Employees. As mentioned previously, overexposure to weld fumes caused by equipment malfunctions can cause a wide range of health problems. Metal dust particles in welding fumes are an eye irritant and a leading cause of eye injuries in factories. Manganese, the primary metal in welding wire, can cause workers to feel exhausted, apathetic, weak, or headachy. Chronic overexposure to such fumes leads to a condition known as manganism, which is characterized by neurological and neurobehavioral health problems.

Robotic weld cells are equipped with individual hoods and ducting. A central fume extraction system keeps the area clean while providing the needed mobility.

Hexavalent chromium overexposure can cause short-term upper respiratory, eye, and skin irritations. Respiratory tract problems can include inhalation damage to mucus membranes, perforation of septum tissue between the nostrils, and damage to the lungs. The liver and kidneys may be adversely affected as well.

A worker exposed to hexavalent chromium may experience symptoms such as sinus irritation, nosebleeds, stomach and nose ulcers, skin rash, chest tightness, wheezing, and shortness of breath. The greatest health danger associated with long-term hexavalent chromium exposure is lung cancer.

The current OSHA PEL for hexavalent chromium is extremely stringent, at just 0.005 milligrams per cubic meter (mg/m3) or 5.0 micrograms per cubic meter (µg/m3).

Zinc oxide is a pollutant generated by hot work on galvanized steel. Exposure can result in a condition known as metal fume fever, a short-term illness in which severe flu-like symptoms occur after a break from work, such as on the weekend or during a vacation. Due to the delayed reaction, it is often mistaken for regular influenza, so many cases go undiagnosed.

Cadmium is a carcinogen that targets the body’s cardiovascular, renal, gastrointestinal, neurological, reproductive, and respiratory systems. It is infrequently encountered in welding and cutting operations.

It is imperative to know and follow OSHA exposure guidelines for these and other metals, particularly where workers are at risk for long-term health effects.

Machinery. Although employees are always the primary concern, machinery in the shop also suffers when weld fumes and dust get out of control. Virtually every piece of equipment today—welding machines, cranes, robots, plasma cutters—contains a computer. When metal dust accumulates on sensitive electronic componentry, it can cause overheating, short-circuiting, and premature failure. Equipment control cabinets with computers often have multiple small cooling fans on which dust buildup can cause reduced airflow efficiency as well as fan failures. This, in turn, leads to increased repair bills and costly, unexpected downtime. Fume and dust buildup in electrical power components can also cause arc flashes, which are extremely dangerous and potentially fatal to personnel.

Solving the Problem

In the past when weld fumes became excessive, the simple solution was to open the shop door and exhaust the fumes outside. That is no longer an option due to today’s more stringent EPA regulations. If fumes are exhausted outdoors, the air is subject to stringent monitoring under EPA National Emission Standards for Hazardous Air Pollutants (NESHAP) Rule 6X, which is highly applicable to welding shops. If air is contained indoors, it is subject to OSHA requirements, which will usually necessitate the use of high-efficiency dust and fume-capture equipment. You can take several proactive steps to ensure that this equipment is doing the best possible job.

Schedule Regular Inspections and Perform Periodic Service. Verify that dampers are in position, valves are working, and pulse-cleaning systems are functioning properly. Check the pressure drop on filters to make sure it has not exceeded the manufacturer’s recommended limit. Check compressed air pressure and purge the compressed air header, looking for signs of moisture. If you are located in a cold climate, make sure that your compressed air has a dew point that is below the lowest temperature your equipment will be exposed to.

Test Your Dust. If you’re having issues or receiving complaints about air quality, bring in an environmental engineer to perform air sample testing. This will allow you to pinpoint what pollutants are occurring and to determine whether you are below OSHA PEL thresholds. Also, if you haven’t tested your dust for flammability and explosivity, NFPA guidelines call for you to do so. An environmental engineer or your fume collection equipment supplier can connect you with a lab that specializes in explosion testing.

Find a Qualified Equipment Supplier. If you are performing preventive inspections and basic maintenance but still encountering problems, chances are the fume extraction system is undersized or inadequately designed for the application. Bring in an air pollution control supplier who is experienced in welding filtration system applications; who is knowledgeable about OSHA, NFPA, and EPA requirements; and who has the technical resources to develop an engineered solution to the problem.

Identify the Best Type of System for the Job. Three general types of cartridge dust and fume collection systems are at your disposal to clean up welding processes, and it is important to apply them correctly.

Source-capture systems are popular for applications involving small parts and fixture welding. They typically utilize a flexible source-capture arm or a complete enclosure around the operation, such as a glass enclosure around a robotic weld cell. This approach is usually limited to smaller envelopes of about 5 cubic feet or less.

Hoods are often used in a medium-sized footprint—12 by 20 ft. or less. Curtains or hard walls may be added to the sides to create a booth or enclosure, although the ability to use such barriers may be limited by workspace requirements or the presence of other equipment or processes in the area.

Ambient systems that filter all the air in the shop using a central system or multiple smaller collectors are often chosen to serve large areas because they allow a facility involved in multiple operations to capture all the fumes. Varied welding processes, large parts, and stitch welding are examples of operations that are well-suited for ambient collection.

Take a Proactive Approach

Keeping weld fumes under control is needed for regulatory compliance, but that is not the only reason for taking action. There are countless documented cases of workers who are healthier and more productive when the indoor air is clear of fumes. Clean indoor air greatly reduces instances of headaches and nasal congestion, as well as more serious and chronic long-term illnesses. It also prevents that buildup of dust on electrical control panels and circuit boards, inspection equipment, and paperwork, a common occurrence that can interfere with everyday shop operations.

In recent years an increasing number of larger companies with hot-work operations have set their own guidelines for dust and fume exposure—guidelines that are sometimes far more stringent than OSHA PELs. These companies are voluntarily testing and monitoring exposure to ensure compliance with their own self-imposed air quality goals.

Though it may not be practical for every shop to initiate such a program, taking a proactive approach to weld fume control will still enable you to affect your workers and company in a positive way—while avoiding the fines or shutdowns that can result from noncompliance.

About the Author

Jon Ladwig

Metal Processing Market Manager

3505 S. Airport Road,

Jonesboro, AR 72401

870-933-8048