Polylactic Acid (PLA) is a widely adopted thermoplastic, valued for its ease of use and derivation from renewable sources like corn starch and sugarcane. As fused deposition modeling (FDM) printers become common in homes and offices, concerns arise about the safety of breathing the air during printing. Melting any plastic material generates byproducts that enter the surrounding air. This article clarifies the safety of these emissions, focusing on the specific compounds released from PLA filament and the necessary precautions to manage them effectively.
What PLA Printing Releases into the Air
When PLA filament is heated to its melting point (typically 190°C to 220°C), it undergoes thermal decomposition. This results in two primary categories of airborne emissions: Volatile Organic Compounds (VOCs) and Ultrafine Particles (UFPs). The amount of these emissions is heavily influenced by the nozzle temperature selected for printing and the specific chemical composition of the filament brand.
The main VOC released from PLA is lactide, the cyclic dimer of lactic acid and the primary building block of the polymer. Other VOCs, such as acetaldehyde, acetone, and various alcohols and acids, are also detected in smaller concentrations. While the overall concentration of these compounds is low, they contribute to the noticeable, sometimes sweet, smell reported during PLA printing.
Ultrafine Particles (UFPs) are generally less than 100 nanometers in diameter. They are created by the rapid cooling and condensation of chemical vapors released from the molten plastic. PLA printers can generate UFP emission rates reaching into the billions of particles per minute under certain conditions. Because of their extremely small size, these particles remain suspended in the air for extended periods, increasing the potential for inhalation.
Documented Health Impacts of PLA Emissions
The primary health risk associated with PLA printing emissions stems from the Ultrafine Particles (UFPs). These nanoparticles are small enough to bypass the body’s natural defenses in the upper respiratory tract. They can penetrate deep into the lungs, specifically the alveoli, where gas exchange occurs.
Once deposited within the lungs, UFPs may trigger inflammatory responses and oxidative stress in the tissue. Prolonged or high-concentration exposure to UFPs has been linked to potential respiratory issues and cardiovascular strain, as these particles can potentially enter the bloodstream. Studies show limited acute effects, but long-term or chronic effects remain an area requiring further research.
The VOCs released from PLA, principally lactide, pose a lower toxicological risk than the UFPs. Exposure to these compounds typically results in milder, localized symptoms such as irritation of the eyes, nose, or throat. While this irritation is usually transient, it underscores the need for exposure control, especially for individuals with pre-existing respiratory conditions like asthma.
Safety Context Against Other Printing Materials
PLA’s emission profile positions it as a relatively safer choice compared to other common FDM materials. The most significant difference is against Acrylonitrile Butadiene Styrene (ABS), which releases substantial amounts of styrene, a classified hazardous VOC. ABS also tends to generate higher total UFP concentrations than PLA during printing.
PLA filament does not release styrene, making it inherently safer regarding toxic VOC exposure. However, PLA’s UFP emission rates are comparable to materials like PETG. PETG typically generates lower overall VOCs than PLA, but the UFP count can still be substantial. This demonstrates that ultrafine particle generation is a concern across nearly all heated filament printing. While PLA is preferred for minimizing toxic VOC exposure, it is not an emission-free material.
Essential Ventilation and Air Management
Regardless of PLA’s lower overall toxicity profile, proper air management is highly recommended to minimize UFP and VOC exposure. The most effective strategy is to implement local exhaust ventilation, which involves actively removing the air from the printing area and venting it safely outside the building. This prevents the accumulation of emissions within the indoor environment.
A dedicated enclosure for the 3D printer, equipped with an exhaust fan and ducting directed to a window or exterior vent, is an ideal solution. This setup creates a negative pressure environment, containing and extracting the emissions before they disperse. Where external venting is not possible, a filtration system using High-Efficiency Particulate Air (HEPA) filters and activated carbon is necessary. HEPA filters capture the Ultrafine Particles, while activated carbon adsorbs the Volatile Organic Compounds like lactide. Printing should never occur in small, poorly ventilated spaces or bedrooms, as this significantly increases the concentration and duration of exposure.