8 minute read
Meet the Speaker: Charles Fleischmann
Professor Charles Fleischmann talks about the recently identified fire hazards associated with e-micromobility devices, and particularly the scooters and ebikes that tend to be charged in bedrooms across our cities.
Professor Fleischmann is principal Research Engineer at UL - Fire Safety Research Institute, and until recently had been part of the University of Canterbury Fire Engineering program since its beginnings in 1994. His research interests include fire dynamics, compartment fire modelling, performance-based codes, backdrafts, and smoke explosions.
At this year’s Fire NZ Conference, Charley will be speaking on the topic of ‘Quantifying the Fire Hazard of E-micromobility devices’.
Professor Fleischmann has given expert witness testimony in civil, criminal, and family court. In 200407, he has served on the Fire Advisory Panel for the New Zealand Department of Building and Housing and MBIE. He is a Fellow of SFPE, IFE, and in 2011 he received the Arthur B Guise medal for eminent achievement in the advancement of the science and technology of fire protection engineering.
Charley is currently the chair of the SFPE standards committee on Design Fire Scenarios and is the section editor of the fundamentals section of the 6th edition of the SPFE Handbook of Fire Protection Engineering. He has over 100 academic and professional publications and has presented many invited and keynote presentations around the world.
FNZM: What are the hazards presented by eScooters and micromobility devices?
CF: In New York City there’s something like 60,000 people, for example, who are employed on electric scooters to deliver food across the city. People who work in these types of jobs are less likely to have a large home to live in and are more likely to live in an apartment building. These tend to be high buildings.
These folk can’t leave their scooters on the street because they won’t be there in the morning, so they bring them up into their apartments, and it’s when they charge them that they can potentially have problems. If an incident occurs, it really can be quite catastrophic.
In the incident in Wellington a couple of months ago, a man was in his apartment with his mobility device and it started to smell a little odd; he went over to it and the scooter basically blew up in his face and he was left badly burned. Sprinklers activated and controlled the fire.
As the Fire Safety Research Institute (a UL organisation) looks into these events, the first part of it is about assessing how big of a hazard e-micromobility devices actually are, how fast these events can occur, and about the extent to which our conventional sprinklers are able to control these fires.
Sprinklers are not really going to put them out; when they get to this point they’re going to run through their reactions, they’re going to spit out hot or molten bits of metal, and they’re likely to be pretty catastrophic.
FNZM: What, exactly, is ‘thermal runaway’?
CF: It’s not specific to Lithium-ion batteries. Spontaneous combustion, for example, is effectively a thermal runaway, it’s a chemical reaction. There’s other chemistry going on between the two but basically this thermal runaway you see in these batteries is just much, much faster because there is more stored energy in them – incredibly high energy densities.
The term ‘thermal runaway’ is not necessarily new but the mechanism here is very different. These batteries can generate heat much faster than they can give it up, and when that happens, they break down and they go through this runaway chemical reaction where you cannot really do anything to stop it.
Fire Services all over the world are starting to ask the question ‘how do we deal with these?’ – especially when you consider something on the scale of an electric car or a bus.
Some junk yards are refusing to take electrical vehicles of any kind because they just don’t know what to do with them. Even if an EV is involved in just a minor accident, some insurance companies are taking the position that the car’s a write off and are not willing to accept that there may have been mechanical damage to the battery. Mechanical damage to the battery is one of the more common causes of problems.
Causes of incidents can relate to damaged batteries, the poor quality of the original battery, or a third-party replacement battery that may have a different battery management system, making it unsafe to recharge. Other problems are aftermarket chargers that don’t talk very well to the battery management system.
Exacerbating the issue is the fact that if you try to take your motorcycle up in the lift in a 20-storey building, people are likely to look at you sideways and probably complain about you bringing your motorcycle in because of the obvious hazard. But if you come in with a small eScooter or eBike, nobody is likely look at you sideways.
Nobody wants to park their eScooter outside: they can’t charge it outside, and if they leave it outside it’s not going to be there in the morning. So, do we provide storage for these, and if we do that then they need to be sprinklered, and they need to be fire separated, so we need to design for that?
Similar questions are being asked about carparks for EV. The problem is, if a fire event were to occur in a carpark it’s a problem, but no one is expected to be asleep in a carpark and the occupants can easily evacuate. So, it is a problem for the fire service more so than the occupants. If my micromobility device is charging in my flat then it’s likely to be charging in a bedroom or lounge, and the occupant may be sleeping in there.
The smoke alarm will go off once the event starts, and five to ten seconds later the device may explode. We don’t consider these to be really survivable events if they happen in your room under the wrong conditions.
These events are not that common, but risk is the product of consequence and likelihood. The likelihood is low, but the consequence is incredible, so that’s what makes this a high-risk situation. When these things start to get into thermal runaway you’ve got a real problem.
FNZM: What are some of the potential ways of managing that risk?
CF: What we do know is that it appears that sprinklers can deal with the fires, but I don’t think that these devices should generally be in a normally occupied space, especially where people are not awake. What we need to do is to start looking at what we do with our buildings where there are people who have these devices. They should be in a fire separated spaces and if we expect to be charging multiple devices there should be sprinklers. If we don’t do this then we can expect some severe fires.
Where these events have occurred in bike shops, they’ve burned out the entire shop due to one device combusting and then causing the others to ignite and burn. Thus, it’s probably not a good idea to have a building with 50 eScooters in them, especially if they’re being charged when we have not designed for it. This is a new hazard, and we have to design to deal with it.
This is only about a three or fouryear-old problem, and New York is just now bringing in local ordinances to regulate what batteries can be brought into buildings. Batteries will have to go through testing and achieve an approval rating. I suspect that regulations may be adopted to prohibit e-micromobility devices from multi-family buildings, but it’s one thing to put such rules in place and another thing to enforce them.
This is very much an emerging fire problem. It’s not easy to find space within cities to store and recharge the devices– and less easy inside existing buildings –so it’s a matter of how we manage this going forward because we’re going to need parking places and charging stations. We’ve jumped headlong into this, and we don’t really have the infrastructure for it.
At this point, there’s a few UL standards out there with performance criteria relating to the testing of batteries, but it’s very much an area where we’re still learning.
It’s great to see that sprinklers work. They don’t necessarily put out the battery fire but what they do is that they keep the fire contained to the mobility device. They’ll wet the sofa around it, they’ll wet the carpet and everything else in the vicinity such that we didn’t observe any fire spread beyond the device itself in the tests we’ve done.
These tried-and-true methodologies work very well, but unfortunately it all happens so fast that smoke detectors aren’t very helpful. They’ll help people outside of the room where the device is but when these devices go up in flames, they have the potential for blowing out windows, and there can be a large fireball that accompanies some of these failures and toxic products that are being released.
How immediately fatal these might be is a question that’s being studied right now. It’s not an easy question to answer in such a short-lived event. It’s very hard to analyse the environment, especially in sprinklered environments. It also depends on how close the person is sleeping next to the device in their bedroom.
People who are likely bringing these devices into their bedroom to charge them are not likely to have large bedrooms with ensuites; they’re going to be small rooms, and that does not bode well for the person in the room.
