CTA to install activated carbon filters on eight 5000-Series railcars to mitigate harmful odors

The Chicago Transit Board has approved the awarding of an agreement with Sandbox Carbon to advance the piloting of activated carbon filters installed on eight Chicago Transit Authority (CTA) 5000-Series railcars to mitigate the smell of cigarette smoke and other odors that negatively impact the customer experience as part of CTA’s Innovation Studio. The new filters include substantially more activated carbon than traditional HVAC filters. 

“We are excited to move forward with this pilot for Innovation Studio,” said CTA Acting President Nora Leerhsen. “We employ a multifaceted approach to confronting the issue of smoking aboard CTA buses and trains, including in-system campaigns and working closely with local law enforcement and security personnel to execute anti-smoking missions. This pilot complements those efforts and seeks to use technology to enhance air quality in our railcars.” 

CTA says it has experienced a significant increase in the number of people smoking on vehicles during the past few years and that smoking on transit vehicles is not only a violation of CTA’s Code of Conduct, it also degrades the rider experience and creates a strong incentive for riders to choose modes other than transit. Additionally, smoking causes lingering impacts on air quality that can affect the health of vulnerable populations, such as seniors and children. 

The agency notes the pilot complements its ongoing efforts to combat the issue of smoking on trains and buses, which includes working closely with local law enforcement and security personnel to confront the issue in real time through strategic anti-smoking missions in which violators are issued citations; plus ongoing amplification of both visual and audio reminders that smoking is prohibited. The pilot aims to help mitigate the impact of second-hand smoke. 

Last summer, CTA’s Innovation Studio problem launched a problem statement seeking solutions to help mitigate the smell associated with smoke and other unpleasant odors. CTA sought solutions that were low maintenance, easily installed and capable of performing in a variety of outdoor weather conditions. The agency says its railcars in particular present a challenging environment for retrofitting new equipment, as solutions needed to: 

• Be resistant to vandalism and avoid obstructing the cabin to maintain passenger capacity. 
• Have little impact on airflow to prevent excess wear on the HVAC system. 
• Address odor. CTA notes that typical HVAC filters can capture harmful particles, but many gases responsible for odors can pass through. 

According to the CTA, the filters will be installed in the return air ducts, which pull air from the cabin for the HVAC system and of which there are four per railcar. Each filter will have a custom-designed protective metal grate to prevent debris from entering. To monitor performance of the filters throughout the pilot, CTA will also install two state-of-the-art industrial air quality sensors in each railcar that monitor two common byproducts of cigarette smoke. The sensors will also monitor air flowing through the HVAC system. 

With this agreement, CTA will fund the one-year pilot with a stipend not to exceed $65 million. CTA anticipates installation of the custom filters beginning this spring following a baseline air quality test to help compare the effectiveness of the new filters. The agency notes it will also evaluate the time it takes for the filters to completely remove the odor from cigarette smoke in the air and ensure the filters remain effective for the full period between maintenance cycles. 

Sandbox Carbon is a small Chicago-based firm that specializes in scrubbing pollutants from fossil-fuel combustion exhaust sources and turning it into inert minerals. According to the CTA, Sandbox Carbon is applying techniques they use in the construction industry to scrub fossil fuel combustion exhaust to the transit context. In addition, Sandbox Carbon will be able to reuse the filters removed from the CTA rail cars for less demanding applications even when they are no longer effective for mitigating cigarette smoke. Sandbox Carbon will be working with the women-owned Chicago-based metal working shop FosterWorks for fabricating the custom stainless steel filter enclosures. 

“Sandbox Carbon is thrilled to partner with the CTA on a pilot project that addresses air quality for transit riders,” said Sandbox Carbon CEO and Co-founder Aaron Rose. “This project will test our advanced odor control technology while fitting seamlessly into existing CTA operations, helping make public transportation more comfortable. We thank the Chicago Transit Authority for its commitment to testing new solutions that elevate public transportation for all.”