Editor’s note: Part 1 discusses industrial air quality in the aerospace industry. Part 2 in the July 2017 issue will discuss solutions to air quality challenges.

While nearly all manufacturing industries have air quality concerns, the materials and processes used in aerospace present special challenges. From engine rework to extrusion of aluminum support components, each aerospace manufacturing process has its own set of indoor air quality (IAQ) challenges. If particulates generated by welding, blasting, grinding, or machining are not controlled, they will quickly cause problems for worker health and safety, product quality, and in some cases, regulatory compliance.

Hidden headaches

Aerospace manufacturing companies must comply with Occupational Safety and Health Administration (OSHA) regulations (or applicable regional/local regulations if outside the U.S.) for indoor air quality. Regulations set maximum permissible exposure limits (PELs) for certain compounds and elements released into the air during manufacturing. Exceeding PELs can subject companies to large fines.

However, the costs of poor air quality go beyond regulations. Failure to control fumes and particulates negatively impacts companies in a variety of ways. including:

Worker productivity – Poor IAQ has been estimated to cause six additional lost workdays per year for every 10 employees. OSHA estimates that worker absences and reduced efficiency from poor air quality cost companies $15 billion annually.

Blasting processes used during engine rework often use toxic aluminum oxide or silica-based materials.

Retention and recruiting – In a recent survey commissioned by Advanced Technology Services (ATS), 39% of aerospace companies reported that skilled labor shortages are having an extreme impact on their businesses. For manufacturing as a whole, The Manufacturing Institute and Deloitte anticipate a shortage of 2 million skilled workers by 2025. For younger workers, the work environment matters, and that includes air quality. Aerospace companies competing to recruit welders and other skilled tradespeople will find that a clean, pleasant environment will pay dividends through lower turnover and more successful recruiting efforts for in-demand workers.

Product quality – Uncontrolled particulates can product quality problems if they permeate sensitive areas such as paint lines or infiltrate electronic components.

Combustion risks – Many of the dust types produced by the aerospace industry are highly combustible, including aluminum, titanium, and magnesium. These dusts have Kst ratings (a measure of combustibility) 10x larger than wood dust, making them extremely dangerous if allowed to accumulate in the air.

Of course, the most serious problem faced by companies with uncontrolled fumes and dust are the risks to worker health and safety.

Manufacturing processes

Different processes produce different kinds and levels of particulates, giving each process its own exposure risk profile.

Welding – Manual and robotic welding are used in the manufacture of aerospace parts, and the characteristics of fumes generated by the welding process can vary widely. The toxicity and the total volume of fumes generated depend on three variables:

  • Type of welding process
  • Base metal and filler metals used
  • Composition of the welding rod

Weld fumes can contain toxic elements and compounds, such as nickel, copper, vanadium, molybdenum, zinc, and beryllium. These fumes are made up of tiny particles that are inhaled deeply into the lungs, where they have both immediate and long-term impacts on worker health. Acute effects of exposure to weld fumes can include shortness of breath and respiratory irritation; eye, nose or throat irritation; or nausea. Long-term exposure to hexavalent chromium (hex chrome), manganese, and other elements can lead to chronic or deadly exposure effects.

  • Hex-chrome fumes are generated from elemental chromium found in welding consumables, typically when welding stainless steel or other chromium-containing alloys. Overexposure to hex chrome can cause asthma, eye irritation and damage, and ear drum perforation. A known carcinogen, hex chrome is associated with elevated rates of several kinds of cancer.
  • Manganese is found in virtually all welding wire and is in many base materials. When it is heated, it reacts with oxygen in the air to form toxic and combustible fumes. Chronic exposure can cause neurological damage (called manganism) that mimics multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), or Parkinson’s disease.
  • Overexposure to weld fumes can also cause a serious condition called metal fume fever, or welding sickness. Metal fume fever causes non-specific, flu-like symptoms such as fever, chills, nausea, headache, muscle or joint pain, shortness of breath, and fatigue. With continued overexposure, the illness can progress to shock or convulsions, requiring immediate medical attention.

Machining – Metal processing often requires lubricants, which create fine oil mists that can be invisible. As the mists settle on surfaces, they can create slip and fall hazards for personnel, and have health impacts when inhaled. Depending on the size of the particulates and the chemistry of the lubricant, extended exposure may lead to asthma, chronic bronchitis, chronically impaired lung function, fibrosis of the lung, and cancer.

Cutting and grinding – Larger particulates from cutting and grinding don’t make their way as deeply into the lungs as the fumed particulates from welding, but the large volume of dust produced by these applications presents special health hazards. Fiberglass, metal, glass, plastics, and epoxy resins can all cause respiratory irritation. Some materials are also carcinogenic when inhaled. Newer materials used in the aerospace industry, including carbon fiber and composites, are associated with skin and respiratory irritation, contact dermatitis, and chronic interstitial lung disease. High-tech nanofiber materials present special risks when cutting and grinding due to the small size of the nanoparticles that have the potential to make their way deep into the lungs and cross into the bloodstream. The health impacts of inhaling nanoparticles are not yet fully understood.

Oil mists produced during machining can lead to asthma, chronic bronchitis, chronically impaired lung function, fibrosis of the lung, and cancer.

Blasting – One air quality hazard unique to the aerospace industry comes from the blasting processes used to clean and refurbish engine parts to meet Federal Aviation Administration (FAA) regulations. The blasting process used to clean accumulated debris off engine components commonly uses hazardous materials such as aluminum oxide. In addition to being a combustion hazard, aluminum oxide exposure is linked to eye, nose, throat, and lung irritation and central nervous system effects. Materials may contain silica, which is implicated in lung cancer, chronic bronchitis, and kidney damage. OSHA recently cut PELs for respirable crystalline silica in half, and companies using silica-based abrasives must comply with the new regulations by June 2018.

Better IAQ

Fortunately, there are steps that you can take to ensure that a facility not only meets minimum regulatory requirements but is prepared for any changes that may come in the future. Meeting current OSHA PELs is a necessary start, and many aerospace companies are moving toward stricter internal standards for IAQ to meet productivity and sustainability goals. The American Conference of Governmental Industrial Hygienists (ACGIH) has developed voluntary exposure guidelines based on rigorous science, which are rapidly becoming internationally recognized best practice for the manufacturing industry.

A well-designed air quality system can protect companies from legal liability and government fines while improving worker health, satisfaction, and productivity. A qualified air quality system designer can help aerospace companies find solutions that balance costs, regulations, and goals. We’ll take a closer look at the mitigation options in our next IAQ article.



About the author: Gordon Diener is an application specialist for RoboVent, a provider of ventilation and filtration systems for manufacturing facilities. Diener can be reached at 402.616.3574 or gordon.diener@robovent.com.