The smell of roasting coffee is one of the most universally pleasant aromas in the world. It's warm, familiar, and signals something good is about to happen. But inside the facilities producing that aroma, workers are breathing a complex mixture of volatile organic compounds, some of which carry serious respiratory health risks with repeated daily exposure. A closer look at the science reveals an occupational air quality problem that the coffee industry is still working to address.
What coffee roasting actually releases into the air
Roasting coffee beans is a chemical process. Green beans are transformed by heat into something aromatic and complex, and that transformation involves the production and release of over 850 individual compounds, many of them volatile organic compounds that become airborne in the production space.
Among the most concerning are two alpha-diketones: diacetyl and 2,3-pentanedione. Both occur naturally in roasted coffee. Both are also used as added flavorings in flavored coffee products. And both have been linked to a severe, irreversible lung disease called obliterative bronchiolitis, characterized by scarring of the small airways, persistent cough, shortness of breath, and lung function that does not improve after leaving work.
Obliterative bronchiolitis was first identified as an occupational hazard in microwave popcorn and food flavoring manufacturing workers. It has since been confirmed in workers at coffee roasting and packaging facilities. A case has also been reported in an individual in India who worked for 20 years roasting and grinding coffee before developing respiratory symptoms.
What NIOSH found when they measured worker exposures
A comprehensive exposure assessment study by LeBouf et al., published in Frontiers in Public Health in 2020 and conducted through the NIOSH Health Hazard Evaluation program, collected more than 1,400 air samples across 17 coffee roasting and packaging facilities, including 10 associated cafés. The findings were specific and significant.
In facilities that produced flavored coffee, 95 percent of production worker air samples exceeded the NIOSH Recommended Exposure Limit for diacetyl of 5 parts per billion, and 77 percent exceeded the limit for 2,3-pentanedione. The geometric mean personal full-shift exposure for production workers in flavoring facilities was 21 parts per billion for diacetyl, more than four times the NIOSH limit.
Even in non-flavored coffee facilities, exposure levels were not consistently safe. Production workers at those facilities had geometric mean diacetyl exposures of 5.6 parts per billion, just above the NIOSH limit. Packaging workers showed geometric mean exposures of 8 parts per billion. The study found that background concentrations of diacetyl and 2,3-pentanedione increased measurably over the course of a work shift in production spaces, indicating insufficient ventilation to clear the accumulating compounds from the air.
Grinding was identified as one of the highest-exposure tasks, because grinding releases the volatile compounds trapped within roasted bean structure into the air at a high rate. Task-based sampling during grinding found geometric mean diacetyl exposures of 26 parts per billion in non-flavored facilities and 30 parts per billion in flavored facilities. Short-term peak exposures during grinding and flavoring were orders of magnitude higher than the full-shift averages.
Why the risk extends beyond flavoring workers
One of the important findings in the NIOSH research is that exposure risk is not limited to employees who work directly with liquid flavoring. In facilities that flavored coffee, even non-production and administrative workers, people not directly handling the product, showed geometric mean diacetyl exposures of 11 parts per billion, well above the NIOSH limit. The compounds dispersed throughout the facility.
Baristas in café settings attached to production facilities were not exempt. While their geometric mean full-shift exposures to diacetyl and 2,3-pentanedione were below the NIOSH limits, 67 percent of café workers exceeded the combined mixture index for both compounds, and the 95th percentile exposures were above the limits. Workers at the espresso machine, pulling shots and grinding fresh beans throughout a shift, accumulate exposure that adds up.
What good industrial hygiene looks like in this setting
The NIOSH researchers were direct about the hierarchy of controls that should apply in coffee roasting environments. General dilution ventilation alone is not adequate to control toxic chemical emissions at the measured concentrations. Dilution disperses compounds through a larger air volume but does not remove them at the source.
What the research recommends is source control. Local exhaust ventilation at grinding machines and flavoring stations, positioned to capture emissions at the point of generation rather than after they have dispersed into the room, is identified as the most effective engineering approach. Physical separation of high-exposure areas, including grinding, flavoring, and packaging zones, from production support and administrative spaces is described as essential for exposure control. In facilities where those zones share open space with offices or break rooms, administrative workers accumulate exposures that engineering design could prevent.
Process automation that reduces the time workers spend in proximity to open containers of roasted coffee or freshly ground product, and enclosures that allow roasted beans to off-gas in sealed containers before they are opened, are additional engineering interventions the research supports.
What this means for workplace air quality management
The picture the NIOSH research paints is of an industry where the air quality problem is real, measurable, and in many cases not being adequately controlled. Most of the 17 facilities studied were small to medium operations that shared production and administrative space, lacked local exhaust ventilation at emission sources, and relied on general ventilation that was demonstrably insufficient to maintain pre-shift diacetyl levels through the workday.
For facility owners and operators, the research provides a specific action roadmap. Measure actual worker exposures. Identify the tasks and locations contributing most to those exposures. Prioritize engineering controls at grinding and flavoring operations. Separate high-emission areas from lower-exposure spaces. And use respiratory protection as an interim measure while engineering controls are being implemented, not as a permanent substitute for them.
For workers in these environments, awareness matters. Persistent respiratory symptoms, shortness of breath that doesn't improve on days off, or cough that has developed since starting a job in coffee production are symptoms worth discussing with a physician and disclosing the occupational context of coffee roasting work.
Clean air in industrial settings requires more than good intentions
The evidence from the NIOSH study is a reminder that pleasant-smelling air is not the same as safe air. The chemistry of coffee roasting produces real occupational hazards that require real engineering solutions, not just adequate general ventilation or the assumption that because coffee is a natural product, the emissions are benign.
For smaller facilities where comprehensive ductwork installation is cost-prohibitive, layered approaches to air management, including industrial air purification with activated carbon filtration that captures VOCs and chemical gases, alongside source control measures, represent a meaningful step toward reducing the ambient chemical load that workers breathe throughout their shifts. Activated carbon is the technology specifically designed for gaseous chemical capture, addressing the VOC category that drives the primary health risk in these environments.
The iAdaptAir by Air Oasis combines activated carbon filtration with True HEPA filtration, UV-C light, and bipolar ionization in a unit designed for commercial and industrial deployment. It is CARB-certified ozone-free and appropriate for continuous operation in occupied spaces. For production managers and facility operators who want to take air quality seriously while broader engineering solutions are being planned or funded, it is a practical tool that addresses real airborne chemistry. Size for the space: the iAdaptAir 2L covers up to 795 sq ft and the 2P covers up to 1,059 sq ft, with a minimum 4 inches of clearance required on all sides.
The coffee industry has built a deserved reputation for craft, quality, and care. Extending that care to the air quality conditions of the people producing it is the next step.
Shop Air Oasis for activated carbon air purification built for environments where VOCs and chemical gases are a genuine occupational concern. Breathe Better, Live Better.
