NEIDL Ventilation Monitoring Was Temporarily Halted
March malfunction posed no public health threat
A malfunctioning network switch at BU’s National Emerging Infectious Diseases Laboratories (NEIDL) resulted in a shutdown of parts of the lab’s ventilation monitoring system for eight hours on March 21. The malfunction impeded the flow of air out of the Biosafety Level 3 (BSL-3) and Biosafety Level 4 (BSL-4) labs. The event, which was immediately reported to the Centers for Disease Control and Prevention (CDC) and the Boston Public Health Commission (BPHC), was detailed in a draft report by outside engineers Colorado-based Merrick & Company, whose final report is expected within the next several weeks. Once the event had been analyzed, BU also notified the National Institute of Allergy and Infectious Diseases.
The University has suspended BSL-3 research until the outside engineers review recommended remedial work to prevent future ventilation system malfunctions. Gloria Waters, BU’s vice president and associate provost for research, says the University will contact the CDC and the BPHC when the remedial work is complete. “We would want to hear back from them before we start to do research again,” she says.
Waters says the event did not pose a threat to public health because no research was under way, safety protocols were in place, and redundant safety systems continued to operate as intended. She says in both BSL-3 and BSL-4 labs, pathogens are exposed to air only within biosafety cabinets, which have their own filtration system, while a redundant filtration system operates in the rooms containing the cabinets.
NEIDL’s BSL-4 labs are not in use, says Waters, because they have not yet received final regulatory approval, and consequently there were no BSL-4 pathogens or research in those laboratories. (BSL-4 research requires the highest safety levels.) Even if research had been under way, Waters says, “The underlying safety systems, which include airtight seals around the doors, worked as intended, and the malfunction would not have created a public risk.”
Waters says the BSL-3 laboratories, which have been used primarily for tuberculosis research, were closed at the time of the event, and had been decontaminated after the most recent research. “Their pathogens were locked down in freezer storage units as required by safety protocols,” she says. The freezers were not affected by the ventilation system malfunction.
The draft engineering report, Waters, and Gary Nicksa, BU’s senior vice president for operations, gave the following details of the event:
The NEIDL’s ventilation, which is controlled by a Siemens Building Automation System (BAS), runs on a dedicated computer network linked to Siemens control panels that regulate airflow into and out of the NEIDL’s laboratories. At 8 p.m. on March 21, a fiber optic module on one of the network switches malfunctioned, cutting off monitoring of the BAS from the Medical Campus control center. The malfunction also triggered a “network broadcast storm,” a continuous stream of data that was sent to all devices on the BAS network, preventing the control panels from communicating properly and causing them to malfunction.
The ventilation system is designed to maintain “negative” air pressure in the BSL-3 and BSL-4 labs, so that any airborne contaminants stay in the labs until pulled by exhaust fans into HEPA filters that purify the air. On March 21, the BSL-3 and BSL-4 labs’ control panels were working properly until the network malfunction prevented exhaust fans from functioning.
With the exhaust fans off, air pressure in the labs increased. Local pressure monitors in BSL-3 rooms indicated that the pressure had become “positive,” indicating unfiltered air being pushed out of BSL-3 labs. Had research been under way, the local pressure monitors would have alerted researchers to finish work with any pathogens as quickly as possible, remove them from biosafety cabinets, the only place they are exposed to air, and safely store them.
The preliminary report by the outside engineers reported that at the same time, the BSL-4 rooms experienced momentary increases in positive air pressure, and the rooms’ internal containment system responded as designed, isolating the air supply. “The pressure monitors and all the controls for each room are contained on a dedicated room controller” the engineers reported. “The room controller was monitoring the room pressure and reacted to the fan failures by shutting HVAC isolation dampers serving the individual BSL-4 laboratories.” As a result, the BSL-4 laboratories remained airtight on March 21.
“Any pathogens would have been contained,” says Nicksa. “They would be vented and purified by a HEPA filter within the biosafety cabinet where researchers handle the pathogens and another pair in the lab’s exhaust system as an extra safety measure in the event any pathogens make their way from the biosafety cabinet into the lab space itself. We know that this system worked on March 21, and we know that it would have provided an additional margin of public safety had the laboratories been in use at the time.”
By 9:30 p.m., NEIDL safety, facility, and technology staffers had determined that a switch problem likely had shut down the monitoring system. An onsite mechanic physically monitored the air handling units and exhaust fans. At 11:58 p.m., with exhaust fans in the BSL-3 labs still inoperative, NEIDL staff replaced the malfunctioning network component.
By 4:45 a.m. on March 22, a little more than eight hours after the initial malfunction, all network services, BAS communications, and the labs’ air pressure control had returned to their proper operation.
BU asked Merrick & Company, which has offices globally and specializes in biocontainment labs like the NEIDL, to validate BU’s investigation and conduct an outside review of the event and the recommended remedial measures. The firm’s final report will be given to the CDC and the BPHC. According to the draft report, remediation may include, among other things: a hardwire interlock between exhaust and supply fans, to shut down the supplying air handling units anytime the exhaust system is not operating; a new protocol on BAS network switch uplinks to reduce the chance of a network broadcast storm; and increased network monitoring that will notify staff of similar events or to any unusual jump in network traffic.
“Boston is one of the few cities with well-defined BSL-3 and BSL-4 oversight,” Waters says, and BU complied with BPHC regulations requiring that the commission be notified. “We overreport because we want to be totally transparent. And we are satisfied that the redundant safety systems that are in place functioned as expected and that there was never any risk to public safety, which is the most important thing.”
Biosafety levels (BSLs), which range from BSL-1 (lowest risk) to BSL-4 (highest risk), are assigned based on primary risk criteria, including infectivity, severity of disease, and the nature of the work being conducted. Each level of containment describes appropriate laboratory practices, safety equipment, and policies for conducting research with a particular agent. The policies are in place to protect researchers, nonlaboratory occupants of the building, the public health, and the environment.
This is a BU Today story.