We move to agenda item 4, under which we are taking evidence on baseline health protection measures from a panel of ventilation experts. I welcome Dr Hywel Davies, who is the technical director of the Chartered Institution of Building Services Engineers; Dr Shaun Fitzgerald, who is the director of the Centre for Climate Repair at the University of Cambridge; Professor Catherine Noakes, who is the professor of environmental engineering for buildings at the University of Leeds; and Professor Tim Sharpe, who is the head of architecture at the University of Strathclyde. We thank them all for giving us their time.
This is the first of four planned evidence sessions on baseline health protection measures, which are the main tools that we are using to respond to Covid-19. They include the steps that we are taking to enhance ventilation in our homes and workplaces and in settings where public services are delivered. This will be a short scoping session to allow us to consider the role that ventilation will play in lessening the impact of Covid-19, especially during the winter. We will also consider the role that ventilation might play in the recovery phase of the pandemic.
We hope that the session will inform further sessions that we plan to hold as part of our inquiry. We will hear from stakeholders in health and social care services, the hospitality, business and leisure sectors, and schools.
Will the witnesses briefly outline what they think are the main ventilation challenges that we should address as part of our response to Covid and our long-term recovery?
Thank you for the opportunity to speak to the committee.
In the short term, the biggest opportunity would come from getting people to concentrate on what they have and on getting that to work properly. It has become clear in the past 18 months that many buildings have not been as well ventilated as they could have been. Things that should have been working have not worked, and things may not have been properly maintained.
It would be a good start if we could get people to do those things, which need not be hugely expensive or time-consuming. There are some fairly straightforward things that can be done. I believe that the committee is aware of the guidance that the CIBSE has produced along with other organisations such as the Health and Safety Executive.
We could concentrate on getting over basic messages about the role of ventilation. Before the meeting, I looked at the Scottish Government website and found some helpful material. Getting fresh air into buildings is important and, in that respect, it might be worth asking Dr Fitzgerald to talk about the use of windows. Opening a window might seem like a simple and trivial thing to do, but there might be a bit more to it than that.
There is a lot that we can do through fairly simple tasks before we get into a discussion about more complicated matters, but I wonder whether we can turn to Dr Fitzgerald to talk about windows.
Thank you, Dr Davies. Before I bring in Dr Fitzgerald, I note that we live in Scotland, which is very cold, we are now moving into winter and energy prices are increasing astronomically, so I hesitate a little bit at the suggestion that we should open our windows. I understand that we would do so for ventilation, but I wonder whether in reality it will happen when people cannot afford to pay their energy bills.
I will bring in Dr Fitzgerald at this point.
Thank you for allowing us to contribute to this evidence-taking session. I am grateful for that.
For me, there are two issues, the first of which is the need to ensure that spaces are adequately ventilated. We must be absolutely clear that we do not want spaces to be so cold that we lose the battle, particularly with regard to work and educational environments. If they are so cold that people are not able to function or learn appropriately in them, those people might as well be at home.
As a result, we must ensure that spaces are not overly cold. Conversely, though, we have to ensure that an appropriate amount of ventilation is provided, and something that could help greatly in that respect is the use, wherever possible, of high-level rather than low-level windows. That would have two benefits. First, air that comes in through a high-level window will mix with the interior air before it hits anybody, which ameliorates what will otherwise be a fairly cold draught. Secondly, if there are only low-level openings, the air at the top of a room where people might be standing and so on will not be ventilated and displaced. There are health benefits to using high-level windows.
Unfortunately, my experience is that many spaces are not that well maintained. In older buildings with sash windows, for example, it is quite common for the top sashes to have been painted shut, which means that people can use only the lower sash windows. It is very simple—cracking open the top sash windows can provide massive benefits. However, coming back to your point, I stress the importance of not freezing spaces, and we must bring poorly ventilated spaces up to a certain standard to ensure that we do not have major infection hot spots.
The second issue that I would like to highlight is culture. In certain work and educational environments, there has been a huge focus on having a lot of ventilation—sometimes, I would argue, too much ventilation, if it impairs children’s learning. It is great that a lot of attention has been given to ventilation, but it is important that we do not overventilate. In comparison, there are other environments, particularly in the retail and hospitality sectors, where there are challenges in providing ventilation and where the windows can be kept closed, especially as the colder weather sets in. There is a high degree of disparity between different settings in the way that the principle of ventilation is adhered to.
Perhaps Professor Noakes or Professor Sharpe can comment on how to gauge an appropriate level of ventilation through, for example, the use of carbon dioxide monitors.
I think that Professor Noakes has asked to speak.
Thank you very much, convener, and thank you for inviting me to join this evidence session.
I want to make two comments. We have talked about some of the things that we can do about ventilation, but before we even get to that point, people need to know why ventilation matters.
Knowledge is still variable. Some people are still focused on washing their hands and the idea that the virus transmits on surfaces. However, as we have gone through the pandemic, we have learned an awful lot more about transmission. It is likely that the majority of transmission happens through inhalation of the virus. You are at greater risk of that when you are close to somebody, but certain settings—particularly rooms where people are talking or singing for long periods of time or doing aerobic exercise—generate more virus particles and longer-range airborne transmission across a room at more than 2m.
10:45Getting across the understanding of transmission helps people to understand why ventilation matters. It matters more in workplaces, educational settings and other communal settings than it does in homes. If you are at home with only your family, it is less of an issue. You do not need to have your windows wide open all the time if you do not interact with others but, when you have visitors, you should perhaps think about ventilating an environment.
To follow on from the points that Dr Fitzgerald made, you do not have to open windows and ventilate continuously. You can open windows a small amount. You get more ventilation for the same size of opening as the weather gets colder, so you can get away with making—[Interruption.]
I apologise for the background noise. I am by a main road with an open window.
In cold weather, as you reduce the size of an opening, you still get quite a good flow through it. Therefore, you do not need anywhere near as big a window opening in cold weather as you do in warm weather and can open windows periodically. Rather than opening them all the time, you can perhaps open them for a few minutes every hour to refresh the air in a space. That can help to manage the balance between temperature, energy bills and ventilation.
As Dr Fitzgerald indicated, in some settings, carbon dioxide meters might be a good way of managing ventilation. A human breathes out carbon dioxide at a higher rate than is naturally present in the air so, when you measure carbon dioxide in an indoor environment, it gives you an idea of how much of the air in that space was previously breathed by other people—how much of it is exhaled air and how much of it is fresh air. The closer it is to background levels—outdoor levels are about 400 parts per million—the better the ventilation is.
We have looked at some of the data on that and have suggested that, if buildings have carbon dioxide levels of about 800 parts per million or less, that represents quite good ventilation but, if you regularly see values such as 1,500 parts per million or much higher, you should think about improving the ventilation or reducing the occupancy in the space. Carbon dioxide meters can be used for that. You cannot use them in every space but they work quite well in offices, schools and classrooms—spaces that have the same people in them regularly over periods of time.
I will hand over to Professor Sharpe, who might be able to talk a bit more about that.
I agree with all the points that have been made.
One of the challenges about ventilation is that it is at the same time simple and complicated. You cannot see or feel it in the way that you can see or feel thermal comfort, so it is challenging to assess the ventilation of a space. That is one of the reasons that devices such as CO2 monitors can be helpful. They give you some indication of what is going on in a space, which can be useful for, if nothing else, raising awareness of what is going on.
CO2 monitors are by no means a measure of ventilation; they are an indicator. They are a blunt tool but, nevertheless, potentially useful in some situations to help users to manage their spaces. The first port of call is to get people to do what they can to manage ventilation, which includes the issue of thermal comfort. It is important not to overventilate and become very cold, but there should be a reasonable level. It is useful to have a tool that helps you to maintain that level.
Regarding measures, the first is to get building owners and occupants to do what they should be doing to manage the space.
Secondly, we must ask what measures we should take for spaces that are not well ventilated or cannot be well ventilated. That might involve unsticking windows, ensuring that systems are effective and work, or introducing other relatively simple measures.
Ventilation does not have to come from windows. Some spaces have trickle vents that provide background ventilation. As Professor Noakes said, ventilation can be open intermittently; it does not have to be open all the time. In a classroom, for example, the ventilation could be open between lessons to purge the space. That is a useful technique.
Ventilation is one of a hierarchy of measures. Our principal concern is about the spaces that might be more affected by ventilation, which are spaces that are occupied for long periods of time by relatively high numbers of people.
You have made some fascinating points. I have a question about businesses, hospitality businesses and others, that are thinking about bringing people back into offices. How easy is it for normal businesses to get carbon dioxide readings for their premises?
I used to run a company that provided such sensors as part of our standard fare. Sensors typically cost between £100 and £200, depending how many are bought. They are quite readily available. We would not be able to provide 32,000 monitors for all the schools in Scotland in one fell swoop, but they are available.
I urge people to think carefully about the quality of the sensors and the urgency of the timescale. The more expensive the sensor is, the better it is, and less work is required to calibrate it. Some cheaper sensors might be appropriate only for this winter, but that might be suitable as a way of dealing with priorities.
My question is about issues in schools. I have received a number of complaints from teachers. In most of the schools that I am aware of, ventilation is provided only by opening windows. That might be fine in the summer, but it creates for teaching staff and pupils an increasingly uncomfortable environment at this time of year. In many schools, the radiators are close to or under the windows, so the heating is on full blast but most of the heat is going straight out the window. That is bad for the climate and bad for school heating bills.
The First Minister said in the summer that she was providing local authorities with an additional £10 million to support enhanced ventilation in schools. Does anyone have a sense of the likely overall cost of fitting adequate ventilation in schools? If that money was available, how, practically, could the work be done and what would the timescale be? I presume that it would take not months but years to bring every school in Scotland up to an adequate standard.
That is a real challenge and it demonstrates that we have a legacy of buildings that we have not thought very much about for many years. To go back to the earlier point about carbon dioxide monitoring, I note that that can be quite a viable solution for schools for the short term, because many carbon dioxide monitors show the temperature as well as the CO2 level. People can therefore try to use them to balance the environment.
I appreciate that that is a very difficult thing for schools to manage. We probably need to start to think about the strategy for how to identify schools that do not have effective ventilation and about how to start to put together a plan for improving that ventilation over the longer term.
It might be found to be the case that not all schools have issues. For some schools, there will be issues across the whole estate; in others, a very small number of rooms will have issues.
There are other things that can done in the short term. It is possible to use portable air-cleaning technologies that might rely, basically, on pulling the air in the room through a high-efficiency particulate filter, which can remove the virus from the air. They do not ventilate the space, but they will reduce risks in spaces that are harder to ventilate. However, they are ultimately only a temporary solution because they do not ventilate spaces. We know that ventilation is important not just for Covid reasons; it is also important for productivity and cognitive reasons, as well as for general health and wellbeing.
Every school and workplace will be different. There is no simple one-size-fits-all retrofit solution, but there are technologies out there that can be retrofitted—for example, mechanical ventilation with heat-recovery systems. They are often stand-alone systems.
I could not tell members the cost—I have not looked particularly at that—but it will cost money. If we are thinking about public health benefits that go wider than Covid, exposure to air quality, learning outcomes and preparation for what might be the next pandemic as a long-term strategic challenge, perhaps it is time that we thought about long-term investment in some of our buildings. Over many years we have not invested in that legacy.
Buildings should be designed, constructed and maintained to meet building standards. That is the case whether or not we are in a Covid pandemic. An unfortunate fact is that the pandemic has revealed deficiencies in that respect. One of the real challenges is that we realise now that we have very little knowledge of how buildings perform in practice. Buildings should meet regulations, though—that is still non-negotiable.
We have the opportunity to gather information on how buildings are working and then to put in place measures to try to address their performance in general. That includes a wide range of things. It is certainly about ventilation, but it is also about energy. One of the big challenges in construction is that we do not regularly go back and monitor the results of our buildings, so we are flying a little bit blind in understanding performance and its implications.
To go back to the specific question about opening windows and heat going out of them, the preferred strategy if a school can only open windows—I am thinking about the coming winter—is to use high-level windows. The problem is that, if there is a low-level window and a high-level window that is often used, the air will come in through the low-level window and be heated by a radiator that will not only add heat to the air to ameliorate what would be a cold draught, but will cause heating in the classroom. If you are ventilating in accordance with modern building regulations, the classroom then gets too hot—weirdly—and the air then moves to the high-level vent. The problems are changed if you focus on using just high-level vents, in which case the radiator will be a lot more effective and will use a lot less energy.
11:00As director of the Centre for Climate Repair at Cambridge, a lot of my research and work has been on reducing energy consumption in the built environment. I have done a huge amount with schools to get the ventilation strategy right. My first port of call would be to try to use the infrastructure that is already there—namely, opening windows—and to be smart about the way that it is used. If, in the future, there is an opportunity to look at, for example, putting in fan-assisted devices because the opening windows are not the right design or are insufficient, you might want to look into prices. Within the industry, it costs something like £3,000 to £5,000 for the equipment alone to fix ventilation for many kinds of classrooms.
This is the COVID-19 Recovery Committee, so I see this as a bit of an opportunity. Professor Sharpe just talked about the current building regulations. If someone is building a house now, they have to make sure that there is trickle ventilation in the windows, and it has to take into account the size of the room relative to the size of the window and so on. You are right about schools—I, too, have been in some where the windows cannot be opened. That was the case when I was at school a very long time ago, and some of those windows will still not have been opened since then.
There is an opportunity for us as a country to say that we have a problem, and that we know that it will help to transmit the virus in enclosed spaces. A very simple solution for some high-level windows—I am taking in what Dr Fitzgerald said about high-level ventilation—would simply be to put trickle vents into wood-framed windows in older Victorian-age schools. Would it be sufficient to allow there to be heat at the bottom and a trickle vent at the top? Would that create enough ventilation in those spaces?
Would you like me to answer that?
Yes, please.
My experience is as follows. Trickle vents are typically very small, so the amount of ventilation that they provide is probably insufficient for 30 children.
I repeat Professor Noakes’s point that, for a given opening, when it gets cold outside and you are trying to maintain an interior temperature of, say 21°C, you need a lot more ventilation because of the bigger difference in air temperature and density, and because in winter there is more wind blowing.
I urge that we look at our high-level windows to see whether we can get them to function properly. Unfortunately, the situation is revealing a problem in respect of how we maintain and manage our buildings, and the attention that we have paid over the years to ensuring that everything is working properly. The situation is revealing problems in the culture of facilities management of buildings. That is what we need to address, instead of saying that we are going to go and fit trickle vents in windows.
I will bring in John Mason, because he needs to leave for the chamber shortly.
Building on what folk have said so far, I have a couple of questions. First, I am assuming that older buildings might be better in this regard than newer buildings, because their ceilings are higher and they are probably more draughty because they are not as well sealed. I am thinking of public buildings and people’s homes. Is that a fair assumption?
That will depend on the building. In many, the answer is yes—older buildings will have higher ceilings and be leakier, and they will naturally have more ventilation, although in a leaky building the ventilation is often very uncontrolled.
However, one challenge is that some buildings have been retrofitted over the years. Quite often, very old buildings have been retrofitted with UPVC windows, so instead of having windows that open at both the low level and the high level, they have windows that open only at one place. They are cheaper windows. We have often engineered out the original ventilation strategies that were put in place in those buildings.
We need to think through the consequences of something that might have been done from an energy perspective and for cost reasons. It is cheaper to have a window that has only one opening than it is to have a window with two or three openings. That relates to the earlier point that was made about trickle vents. Rather than retrofitting a few trickle vents, we should put some effort into improving schools. It is one thing to take some cheap and quick actions that might reduce an immediate problem, but if we are going to put effort in, we should make sure that we do it properly and not retrofit inadequate trickle vents, say that we have solved the issue but then come back in five years and say that we wish that we had done it differently.
It is worth thinking through what was originally designed for the ventilation strategy in a space—whether that strategy is still applicable, whether it has changed over the years and what we can do to improve it. We will probably struggle most with buildings that were built in the 1960s, 1970s and 1980s, when energy was a big focus and there was a reduction in the size of spaces. It is much harder to get good ventilation in those buildings, so they might be hardest to deal with.
Perhaps it would be worth bringing in Dr Fitzgerald on that point.
I am sorry—I will bring in Professor Sharpe, who has asked to come in.
I will make my points brief. First, the regulations apply to new buildings, but the vast majority of the stock is made up of older buildings that were built to older regulations or no regulations, and which have, as has been pointed out, been changed and so on. There are lots of examples of that.
When we apply measures, they need to be designed in and not just put in as blanket measures. That needs to be undertaken with consideration of the whole performance of the building, including its energy performance. There are plenty of examples of where we have taken single measures—such as forms of retrofit for thermal performance that have not included ventilation measures—which create unintended consequences. It is important that when we think about measures we try to understand the intended performance.
I will go back to Professor Noakes’s comment. In relation to more modern buildings, it is cheaper to build buildings with a shallower floor-to-ceiling height, because there is less wall. Unfortunately, those buildings are not as well suited to the old strategy in Victorian-type buildings in which, with sash windows, you could just crack the top sash open and allow air to come in naturally and mix with enough of the warm room air to ameliorate a cool draught. The higher the floor-to-ceiling height, the smaller the problem of a cool draught is.
Professor Noakes is right that the more modern buildings—from the 1960s onwards—which were built on the cheap and have smaller floor-to-ceiling heights, have more of an issue with draughts. There is then the issue of trying to preheat the air with radiators, which has energy penalties, so assisted mixing or heat-recovery units might be necessary. The more modern buildings are a bigger challenge than historical ones.
I will pick up the regulatory aspect, because a committee member made a comment about the opportunity that might exist there. We have to make a significant effort to improve the energy performance of our buildings and we are aware that we need to think about ventilation. It is important that we take a systematic approach and do not allow people to pick off one issue at a time. When work is being done on buildings to improve their energy performance, it is important that ventilation is also considered.
There is an opportunity, particularly in Scotland, where there is a single system of building verifiers in the public sector. They need to be encouraged to consider the role that they can play, when supervising projects, in ensuring that ventilation is properly considered at the design stage, then properly installed. It is easy to include such measures in the design and to get it signed off, but designs are sometimes altered. The euphemism is “value engineering”, but it is not engineering, nor does it add value, usually. It is usually about reducing costs, some of which are associated with providing important things.
Building verifiers need to be encouraged to see ventilation and energy efficiency as two sides of the same coin. We would then avoid running the longer-term risk of people thinking that they can either have good ventilation or have energy efficiency and lower bills. It does not need to be that way. We can ventilate well and be energy efficient if we think things through systematically. I hope that that is helpful.
If we are okay for time, convener, I will aim my next question at Professor Noakes. I want to follow up on what she said to Murdo Fraser. She talked about air-cleaning technologies and high-efficiency particulate filters, which I am trying to get my head round.
I have an issue with ScotRail, our railway operator. This might be slightly different from the situation with buildings, but ScotRail has some trains with locked windows. They could be opened, but they are not. I asked ScotRail whether it would be better to open the windows, but it said that its artificial air-circulation system is just as good as having the windows open. Is that likely to be true?
It is quite likely to be true. It is difficult to say definitively, because every system is different. It is quite likely that the trains will have a mechanical ventilation system that can provide fresh air that is as effective as opening windows.
The risks on public transport are difficult to understand, because it is difficult to get direct evidence on whether transmission happens on public transport. We can consider the factors that influence risk. One is proximity to people, and public transport, of course, increases that risk. Activity is another factor, and that risk might decrease on public transport because, a lot of the time, people are relatively passive. If the wearing of face coverings is done well, that reduces the risk on public transport quite significantly, because we reduce the amount of virus that is put into the environment.
Another factor is duration. There is probably a relatively low risk—from the perspective of airborne transmission—from very short commuter-type public transport journeys, which are often only 20 minutes or so. We need to think about ventilation for longer journeys, in which people might be in the same carriage as others for several hours. Some trains can, and are designed to, have their windows opened, but those trains tend to be used for shorter-distance commuter journeys. I urge that those windows be open, as far as is practically possible, although that will probably not work in certain weather conditions because people will end up very wet.
Trains that are used for longer-distance journeys rarely have opening windows. Given their speed and the pressure that goes through them, they are not practically designed to have opening windows. They are designed to have a ventilation system that usually results in about eight air changes per hour in the carriage, which means that there is fresh air every seven to 10 minutes or so in that space.
That is helpful.
11:15
I have a quick question. Returning to schools and the short-term, or the here and now, as we head into winter, the Scottish Government has continued the policy that face coverings should be worn in schools, but what is your immediate advice for education authorities? Education authorities have property managers that manage the school estate, but do they have the required skills and knowledge, or do we need to bring in advisers? Earlier, Murdo Fraser mentioned a figure of £10 million, which is not a lot. What would you advise the Government and education authorities to do in the short or immediate term as we approach winter?
My urgent request is simple. Many schools just have opening windows, so we need to make sure that they are properly maintained. Do schools have high-level windows? That is not a skills issue; it is an issue about previous budgets and attention and adherence to those measures. I will let someone else comment on the use of face coverings but, from an estates point of view, my immediate priority would be to look at high-level windows. Subsequently, I would go back to the other issue of making sure that we do not freeze the spaces, and carbon dioxide monitors can help to make sure that we provide enough ventilation, but not so much that we have issues with energy bills and thermal comfort.
As Dr Fitzgerald said, the priority is largely about making sure that what is there is working. In older schools, there are lots of instances of windows being painted so that they cannot open. We need a basic audit of what we have, in order to see whether it is working. If schools have CO2 monitors, they can be used in identifying areas where there might be greater risk of transmission, so that they can focus on those places and see whether something is not working.
Those spaces might never have been very well ventilated, but the schools have not had a reason to find out until now. Professor Noakes’s comment about air cleaners might be one way of dealing with those circumstances. An audit might reveal just one or two spaces that are currently so badly ventilated that it would be better not to use them for a few weeks and to take advice on how to deal with them. Those are immediate short-term ways to reduce risk over the next few weeks and months.
I will be brief, because a lot of the points have been covered. Everybody recognises the importance of ventilation, not just for Covid but for many other considerations, as well as the fact that CO2 monitoring would be beneficial. I am thinking about the practicalities of developing a country where the buildings have good ventilation. As the convener said at the start of the discussion, we know that poverty is a major driver of proliferation of the virus. The practicalities of developing all our buildings so that they have good ventilation is beyond the Government’s budget, so I presume that we are talking about a focus on commercial rather than domestic properties.
I will make two points—one on that question and one about a prior question.
There was a comment about use of face coverings as well as ventilation. It is important to recognise that ventilation is only one mitigation measure for the virus. We must also think about other mitigations in spaces and about how we mitigate at close proximity to people. Ventilation will not mitigate close-range transmission, which is where face coverings and physical distancing come in. We must also think about other strategies, such as requiring people to stay at home when they have symptoms, making sure that we have good testing in place and so on. Those strategies limit the risk of having infected people in a space.
We must recognise that making our buildings good for the long term is a really big challenge and not something that we can solve overnight. If we do not have an ambition for that long-term goal, it will never happen. That ambition must be tied up with reaching net zero. We have a long-term ambition to reduce emissions and to make our environment more energy efficient in order to reduce our impact on the climate. Ventilation should be tied in with that. When we put heat pumps or insulation into buildings, we must ventilate them at the same time. That should be part of the long-term strategy for commercial and domestic buildings.
There will be a hierarchy with commercial buildings. We must start with the worst ones. The example of schools has come up several times. Some schools will already have good ventilation in the majority of their classrooms, so those are not such a concern. Others will have ventilation that is okay but not great. We could look at what we can do to those in the short term and consider longer-term improvements.
The buildings that we are most concerned about are the ones with truly inadequate ventilation that impacts more widely on people’s health and wellbeing. We should think about a programme for those. The first question should be whether buildings are fit for purpose. I know that there are programmes of building new schools and other buildings. Those programmes should prioritise the buildings that are not fit for purpose. With buildings that are fit for purpose, we should think about the priority spaces where we have to invest.
That is a long-term strategy, and we need ambition to make it work. We have ambition for other things, so I do not know why we do not have an ambition to have healthy buildings. The benefits could be enormous.
We know how to do that—it is not rocket science. We have the tools and technologies to make buildings perform very well, but we do not do that as a matter of course. That is the challenge. There are plenty of ways to address the problem. We should think about a building as a whole system. It should be properly designed, constructed and maintained to care for that system.
The challenge is in no way impossible. The problem is a lack of political will. There is a question about whether our regulations are being properly complied with. There are also important questions about retrofitting. Building regulations do not apply to retrofitting, unless the changes are significant. We should look at that area. There are technical challenges, but there are also significant policy challenges about whether we want to mandate those things.
I thank the witnesses for their time and for their evidence, which has been beneficial. If any of the witnesses would like to share further evidence, they can do so by writing to the committee. The clerks will be happy to liaise with them about how to do that.
The committee’s next meeting will be on 11 November, when we will continue taking evidence on baseline health protection measures.
11:24 Meeting continued in private until 11:31.