The Air On BART is About to Get Better
After a successful pilot, BART will install denser filters throughout its fleet of train cars, part of a multilayered plan for stepped-up system safety as the pandemic plays out.
New Filters
Air filtration has an important role in preventing transmission of the coronavirus, along with vigilant mask-wearing. Filters on BART are in the heating and air conditioning unit underneath each train car.
They’re rated by their ability to block different-sized particles, a rating known as their minimum efficiency reporting value, or MERV, on a scale from 1 to 20. The old MERV-8 filters could trap particles between 3 and 10 microns in size; the new MERV-14’s can capture much smaller particles between .3 and 1 microns. BART engineers sent the pilot filters out for pressure-drop testing to measure their effectiveness.
“We’ve completed the evaluation and gotten the numbers back,” said Ben Holland, Manager of Vehicle System Engineering. The pilot took about six months in order for the testing to occur after a train car had gone through its full preventative maintenance cycle of real-world operations.
Ventilation on BART is extremely robust, with an entire train car’s air being replaced about every 70 seconds. Overall, the air in BART trains at a given moment is about 75% filtered and 25% fresh air drawn from outside the car (it’s 80/20% on legacy trains and 70/30% on Fleet of the Future trains).
What’s Next for BART?
Another pilot, which is testing a ultraviolet UV-C lighting rod inside one legacy train car’s undercarriage HVAC unit, is still in the evaluation phase but looks promising, Holland said. “We’re still monitoring that,” he said. “So far it’s been working well. We’re still trying to figure out how to replicate that into Fleet of the Future HVAC units.”
More good news from the UV pilot, he said, is that engineers have refined the design in order to put two UV-C bulbs instead of one, in addition to using bulbs that are 50% longer than in the original pilot design. “We’ll get three times as much light output – it’s almost like installing three bulbs. We’re still in the process of finalizing the electrical and mechanical details.”
The only hurdle may be finding suppliers. “We are working on the design in-house because if we rely entirely on them to produce a design, it could take quite some time,” he said. “This is urgent and important to us and to our customers.”
BART engineers have had preliminary discussions with scientists from the Lawrence Livermore National Laboratory regarding simulations that can mimic a sneeze or cough to quantify the flow and travel of aerosols, tiny airborne particles that can carry coronavirus or other pathogens.
“We’re in all talks with all kinds of different agencies,” Holland said. “This is being watched and scrutinized all over the world. It’s hugely important for our public.”
Chief Safety Officer Jeff Lau said BART is “actively evaluating many different technologies” that could potentially be used in the transit system to combat the coronavirus.
Robots?
One product, a robot that could run through cars in their off-hours and spray disinfectant, was tested but probably won’t move forward because of difficulties in accessing the trains and moving between them, Lau said. (Trains already are disinfected with electrostatic foggers, which are applied by a human, at night.)
A smaller, Roomba-like device that can vacuum and disinfect at the same time will also get a test run.
“We are open to all different kinds of technologies and innovations,” Lau said. “We are trying to be a leader in the industry in keeping our patrons and employees safe. I’m very confident that our system will be as safe, maybe even safer, than before (Covid), thanks to enhanced cleaning and changes in behavior like wearing masks.”
