少点错误 2024年12月21日
Last Line of Defense: Minimum Viable Shelters for Mirror Bacteria
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本文探讨了在镜面生物灾难威胁下,如何设计经济高效且高防护的避难所。文章指出,尽管预防灾难发生是首要任务,但避难所的准备工作同样重要。核心威胁是镜面微生物的有意或无意释放,通过正压塑料“气泡”和串联高效空气过滤器,可以实现高水平的防护。该方案基于现有技术,成本相对较低,目标是为每人提供每年低于1万美元的保护。文章还详细分析了空气和水中的微生物浓度,并提出了相应的过滤和净化策略。最终目标是,即使灾难发生,也能为人类提供生存机会,等待外部环境恢复。

🦠 镜面生物威胁是避难所设计的核心驱动因素,包括有意或无意的镜面微生物释放,可能导致灾难性后果。文章强调,尽管预防是关键,但准备避难所至关重要。

🧫 避难所采用正压塑料“气泡”设计,并配备串联高效空气过滤器,以应对高浓度的微生物威胁。这种设计基于现有技术,成本相对较低,并能提供14-log的微生物过滤能力。

💧 水源方面,文章建议从古老含水层取水,因为这些水源受地表污染影响较小。对于受污染的水源,则采用热消毒技术,并建议结合长期成本效益考虑,选择更安全的水源。

🛡️ 避难所设计参考了北欧民用核避难所、政府掩体和军事防护单位等多种现有方案,并在此基础上进行了改进。文章还提及了2021年相关领域兴趣的增加,这可能与资金支持和镜面生物威胁的日益增长有关。

Published on December 21, 2024 8:28 AM GMT

Epistemic status: We are moderately confident in the feasibility of serially filtered shelters for 14-log protection and precise cost estimates, and high uncertainty about how mirror biology might develop in the real world.

Originally published on the EA Forum. Minor edits for LW adaptation.

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Summary and main take-aways

pictured: a cut-through view of an inflatable shelter with a small room, large room, and airlock

My background

I am Ulrik Horn and have worked on these shelters for over 2 years.  I’m considering manufacturing them commercially, and have recently started a company.  I wanted to share my theory of change in case I'm making important mistakes. I'm also interested in talking to people who might want to help, and especially people, whether in the public or private sector, who would be interested in buying one, or know someone that might. The values of the company will be front and center and are Honesty, Responsibility and Family Security - values that deeply align with my own values. The hope is that a clear, continuous focus on especially honesty and responsibility will ensure decisions around communications are made to avoid fear mongering, unrealistic projections of doom and similar “risky” PR strategies. This is why we lean heavily on the precedent of Nordic civilian nuclear shelters while we want to steer away from “prepper marketing”.

Details on threat picture

The key threat we’re concerned about is mirror biology.

Others have done a much better job than I could do of summarizing the findings and explaining the danger of mirror biology, and the team behind the report have also created a short summary article. However, these summaries do not go into much detail about possible defenses, and the technical report doesn’t discuss the possibility of shelters. To be clear, shelters are in no way a desired outcome: they would be a desperate, last-minute effort to save what we could as the biosphere turned hostile.

What’s needed for shelter design is to understand environmental concentrations of the threat. Unfortunately, as the report explains, we’re still quite uncertain how a mirror biology catastrophe would play out. This means we will have a hard time guessing about what environmental concentrations we have to defend against. With uncertainty, it becomes necessary to create high levels of protection. The strategy we employ below is to use upper levels of currently observed “normal” microbial concentrations and then add a safety factor on top of that to represent the risk that, without natural ‘predators’, mirror bacteria might temporarily become overwhelmingly common.

The highest atmospheric concentrations we’ve identified are in connection with dust storms. This makes intuitive sense: soil is some of the most microbially dense widespread material we know of and high winds will bring large amounts of soil and dust into the air. We discuss concentrations in units of Colony Forming Units per cubic meter, CFU/m3.The highest CFU counts recorded during dust events are around 10^7 CFUs/m3.

This is not as conservative an estimate as we would prefer, again due to the uncertainty about exactly how a mirror biology catastrophe would unfold. Mirror organisms would inevitably interact with the complex environment in a multitude of hard-to-predict ways, and if significant vegetation dies this could potentially lead to much higher erosion rates and more frequent dust storms in areas that have not previously experienced significant dust storms. Still, we think 10^7 CFU/m3 is still a generous upper bound when considered over the multiple years the shelter would be in operation.

How would we defend against a concentration of 10^7 CFU/m3?  Air filters are the obvious choice, but how much filtration would we need?  The requirement for removal is to not let a single particle into the lungs or digestive tracts of the inhabitants, because we want to conservatively assume that if this happens the microbe will reproduce, killing the initial host and any other shelter inhabitants.

In microbiology and related fields, due to the extreme numbers of microorganisms as well as their exponential growth, one uses logarithms to talk about sterilization. Reduction by 90% of a microorganism is a 1 log reduction, 99% is 2 log and so on: the logs can be thought of as “counting” the numbers of 9s in the percentage efficiency number. Now, no number of log reductions will give us certainty that no CFU makes its way to the inside; we can only talk in probabilistic terms. Therefore, let us start with the requirement that we want a 1% chance or less that a single CFU is inhaled by an inhabitant.

Consider a shelter designed to protect four people for one year.  Each person needs at most approximately 20m3/day (see e.g. table 6-5 here) of fresh air, but assume 40m3/day to be conservative.  This would require an air intake of around 160m3/day, or approaching 10^5 m3 over a year.  At our target average atmospheric concentration of 10^7 CFU/m3 our filtration system will be faced with 10^12 CFUs.  To have just a 1% chance of passing a CFU through we would need it to pass fewer than one in 10^14 CFUs, a 14-log reduction.  This is a staggering reduction, but as we discuss below we think this is possible with sequential filtering.

Water concentrations are similarly hard to estimate, and in current shelter work we have accounted for consistent, extreme levels. Note that for water, concentration numbers can be much, much higher than for air (at some point the definition of “water” is cast in doubt - it could be mostly microbes mixed with a bit of water!). For example, in water just downstream of large amounts of feces or decomposing carcasses we would expect to see something in the range of up towards, and perhaps sometimes above 10^8 CFU/ml. The latter scenario could be a common occurrence in a worst-case mirror biology catastrophe. With heat sterilization, we think it is reasonable to assume one can sterilize to 10 logs, probably even quite a bit more. But this would be insufficient for extremely polluted water over longer time periods. Therefore, we would recommend sourcing water from an old aquifer - these can take more than 100 years to receive significant intrusion from the surface and on a per liter basis, especially over the long-term, such clean water supply is extremely cost effective compared to other methods of delivering safe water. 

Even if we built a shelter that could keep out this level of environmental hazard, we think this is unlikely to be a scenario where humanity can simply stay put and wait for the problem to go away. We see shelters meeting these requirements as only one component of a larger response, allowing more people to survive to a time when, through efforts elsewhere, it’s possible to live outside these shelters again. 

One question that is probably high on people’s minds and that is also very relevant to shelter work: Is it likely that we will as a global society develop dangerous mirror biology science? To this I can only say I really hope that we can keep a lid on this, but I want us to be prepared in case that’s not how it goes.

Details on the shelters

The current shelter design is fundamentally uncomplicated: A positively pressurized plastic “bubble” supplied by serially filtered air. That extreme levels of protection can be achieved with simple and relatively affordable protection makes this solution attractive.

pictured: a view of a complete but empty inflatable shelter with a small room, large room, and airlock

These shelters are a direct descendant of a lot of different strands of previous shelter work. They build on the civilian nuclear shelters in Northern Europe, continuity of government bunkers in the US and Russia, Collective Protection Units used in the military, and concepts of civilizational shelters or refuges discussed on this forum by various people since 2014. However, around 2021 there was an increase in action around this idea in EA and EA-adjacent circles. It is unclear to me exactly what drove this increased interest: it could have been the seeming availability of FTX funding, the gradually rising prospect of a mirror biology catastrophe, or something else. This post describes work that directly built on that increased activity, encouraged by previous suggestions that shelters be pursued, using previous work as input and announced in a previous post I wrote declaring the commencement of my work on the topic.

The shelters were conceptualized as an answer to the following question: what would be the absolutely cheapest way to construct a space that had 14-log protection in terms of atmospheric aerosols? When the question is phrased this way a solution presented itself: serial air filters supplying a positively pressurized plastic bubble tent, inside a larger existing structure for protection from the elements. 

While the concept of a positively pressurized shelter isn’t new, we’re not aware of earlier work that uses serial filters.  Moreover, this concept of a shelter is extremely minimal, which has two additional benefits:

Serial filtration has been shown to achieve extreme levels of performance. During the Cold War there were plants that generated plutonium dust and needed to vent dust-containing air to the environment. Due to concerns about radioactive pollution, air was passed through a series of HEPA (protection factor of 2000 which is 99.95% efficient) filters and the efficacy of this treatment was finally tested at the Los Alamos lab that demonstrated an average of 12-log performance and a worst-case performance of 10-log. We are therefore fairly certain that this performance can be extended to 14-log and perhaps even higher.

For the positive pressure, no similar empirical experiments at the required level of performance have been found. But talking to an engineering professor in cleanroom technology who has investigated contaminant transport into cleanrooms, they thought it impossible for even a single particle to enter a positively pressurized space through the space envelope. Moreover, calculations were performed on diffusion speeds and likelihoods based on established physics and these similarly showed that practically speaking, the chance of a particle entering “against the flow” through a 0.5mm wide and 2mm long hole was, for all intents and purposes zero.

An important factor here is wind. Simple calculations with Bernoulli’s equation show that one can quickly get pressures of more than 100 Pa with wind gusts that appear with some frequency in most locations. If the pressure generated by wind exceeds the pressure differential from the inside to the outside, there is a significant risk that outside aerosols might be pushed inside. This is why these shelters are envisioned being deployed inside a larger protective structure. Due to the inflatable plastic structure, there are few requirements on such spaces and they can be anything from garages and large living rooms to farm buildings and warehouses. 

pictured: A fully equipped shelter along with two inhabitants deployed as intended inside a larger structure (in order to protect from particle intrusion by wind gusts)

While the main concept of these mirror bio shelters is a smaller positively pressurized space supplied by serially filtered air, there are more components needed for long-term survival. 

Above, the following items have been covered:

In addition, the following items are likely required:

On protective gear, the highest protection factor gear found has been >50,000 protection factor which is 4-5 log of protection. Note that this is far short of the required 14 log for the protection. Some of this gap can be bridged by limiting the amount of time spent outside (if needing to survive for only 1 hour, the required log reduction would be “only” 7 log). Also, if combining a suit with protective tunnels to transfer personnel between habitation and transportation, it might be that the tunnel + suit will offer sufficient protection. Moreover, these suits will be supplied by stored, compressed air so the tunnels could be filled with VHP, further increasing the log reduction.

For power, it is hoped that the government will protect the utility workers so that power will be available via the grid. But in case one would like to prepare for the eventuality that this fails, or even to have protection against interruptions, an off-grid system might be good. The most cost effective set-up will depend on geography. In areas with sufficient sunshine during winter, solar and batteries will provide the main bulk of power while a propane generator will provide power during any prolonged periods of cloud cover. Note that the most costly components of an off-grid system (solar and batteries) can be used during regular periods to offset utility bills and therefore partially (or in special cases fully!) pays for itself.

For food, it is fortunate that the Church of the Latter Day Saints has been developing cost effective ways for long-term storage of food. There is some uncertainty about especially vitamins and oxidation of fats, but it is hoped that refrigeration will go some way to solve this issue. In any case, based on a growing base of information from space missions and Mars analogues, it seems very wise to make a small investment in an ability to grow plants indoors. Organic waste will be ample, and there will be water. As such, at least for some time, it should be possible to at least grow some foods that could help alleviate especially problems around vitamin deficiencies.

Other items are important too, even though they might not directly relate to the rule of 3. Long durations of isolation places very high burdens on people and the lockdowns many experience during COVID was quite benign compared to being sealed in bio shelters for months, if not years. Luckily, Tereza Flidrova has done excellent work on what is needed to increase the likelihood that significant psychological problems do not happen and the shelter design should heed as much of this advice as possible. Luckily, due to the flexible and low cost material, many such design aspects can quite easily be accommodated at only modest increases in cost of production.

While the solution seems technically robust, there remains uncertainty around several areas which demonstrate the need to as soon as possible deploy and test these units:

The first version of the shelter structures, “plug-and-play” ready are expected to retail for $39k. The structure would include the following components, with estimated cost:

The difference between retail price and the sum of the component cost is for design, construction, company overheads, return to investors, etc. Note that the earlier $10k/person number does not include anything but material costs. This is because it is unclear how, in a “war time mobilization” by the government to make as many units as possible in the early days of a crisis, how the cost of manufacturing etc. will be accounted for. The design might even evolve to be simple enough for people to make such shelters by themselves out of commonly found and varied plastic materials and HEPA filters repurposed from other uses. This would indeed be a highly desired outcome and I commit to always optimize for societal goods. For example, if a part of the shelter was to be protected by IP held by the company set up, I would do all I could to let individual households use the design freely. If the company is successful I will also be careful about what investors to bring on board as a disastrous outcome would be one where there is an unfolding mirror bio catastrophe but owners of patents refuse to share the design with the wider world in order to maximize profit. An ideal outcome would be to have a high level of governance and transparency which is why one board member has been chosen specifically for this purpose. The hope is also to find biosecurity impact investors, where one potential benefit of this solution is that if mirror bio looks more likely to go wrong, demand for these shelters will increase which also increases the returns to shareholders. If these shareholders have a consistent record of donating to biosecurity or similar causes, one can hope that this business would be able to generate needed cash during a biosecurity crisis which can then be donated to other, urgent priorities to help avert the crisis.

Beyond this, the following purchase prices (note that power and food can be consumed and as such might at least partially “pay for itself”):

Lastly, in order to exit the shelter during low atmospheric concentrations, the following would be needed in additions:

It is when the material costs above are summed that one ends up around the $10k/person mark:

3900+10300+4000+2000+12000+(1200*6)+2000+5000=$46400 total or 46400/6=$7733/ person. Note that the inhabitant number here has been increased to 6. This is because an assumption, based on research into inflatable construction, is that these shelters can be made much less luxurious than bubble hotels (that people spend $200/night to stay in!). Therefore, less luxurious units can be made much larger for the same price and easily house several more people.

A note on costs above: I think all these costs represent something closer to median costs, especially as some of the more expensive components like food, power and envelope are based on actual prices and quite detailed analysis. I think there is some scope for costs to drop with volume of production, optimizing component design and innovations. There is also a chance that these units might end up more expensive. However, as the product is simple and the expensive components are already available for retail sale, it is hard to see how they could increase substantially. That said, there might be challenges with e.g. having high levels of certainty around maintaining positive pressure which could e.g. lead to much more expensive, precision, variable speed fans and a need for more sophisticated pressure sensors and controls, especially during entry/exit. It is expected that during construction in the coming weeks, such issues will be discovered and solutions seem within grasp as the working principles of this intervention are simple.

Power might also be more expensive, and in some cases significantly more expensive in locations with less sunshine, and especially if heating beyond electric blankets are needed. However, the suggestion with the intervention, if cost is a concern, is that gov’ts will focus deployment in locations where the climatic conditions are more benign. Luckily, this often happens to coincide with large population centres as people often chose to settle where the weather is better (e.g. California, Southern Europe).

Lastly, as the currently designed units planned for immediate sale is based on comfortable bubble hotel construction and design, it is imagined that in certain jurisdictions, these units can even be used during “peace time”, when there is no imminent crisis. For example, they could be put up on a lawn to provide space for guests or teenagers. Or if one has a remote piece of land, as a weekend getaway. As such, the hope is that this will sufficiently increase the attractiveness of these units so that a number of them are actually deployed, marking real-world progress on an “end-to-end” x-risk intervention: Advisors have speculated that if a sufficient number of these units are deployed, this might have already decreased existential risk by some amount, especially if we can get some distance beyond ~100 units over a not-too-large geographical area. And given the relatively modest philanthropic funding of this project to date, this effort might hint at a cost effective, “end-to-end” x-risk reduction, especially if gov’ts take the necessary steps to prepare to produce these units at scale. Thus, the ideal scenario is one where governments are ready to produce thousands of units so not only a minimum viable population survives, but enough people to carry on the most critical, welfare-generating parts of our societies. 

A bit more context: Funding until now + future funding

The work described here has been funded from a number of philanthropic sources.  We’ve been planning based on relatively limited philanthropic-scale funding, thus the decision to set up a for-profit company to see if private capital can be leveraged to make progress on mirror bio shelters.

If significantly more philanthropic funding were to become available, we don’t think we would advocate for more expensive fortified designs contemplated in the past:

The road ahead

At this point it might be worth revisiting the epistemic status of the topic of how these shelters would actually be used in a mirror biology catastrophe. Put succinctly, the epistemic certainty drops significantly when speculating on the road ahead. So far, these units seem to physically offer significant protection and they might be tolerable from an inhabitant well-being perspective although larger units would be desired. But both because there is inherent uncertainty about exactly which mirror pathogen would be the concern, as well as how any mirror pathogen would interact with the environment it is really hard to say what surviving such a catastrophe looks like. For example, might there actually be periods with sufficiently low atmospheric concentrations so that people can be outside with only 2-3 log protective PPE? Also, much more work would be needed on trying to give any survivors more long-term strategies such as where to replenish supplies of essentials such as food and disinfectant. But one step seems clear: We need to take these shelter plans from paper to reality, and start producing, testing and improving on these shelters.

On this latter, more imminent point, I will continue working on shelters in the following way, if things go well:

    The first unit of these shelters is planned for construction in early 2025. It will be subjected to basic testing such as “can we maintain a stable pressure in this space while in use?” and “how easy is it to integrate an “industrial”, cleanroom-type ventilation system with a basic inflatable plastic structure”, etc.I will then judge interest from various groups (gov’t, philanthropic, private) in these shelters. If there is enough interest it might be feasible to run a company that constructs and delivers these shelters. Simply having such an organization provides protection: There would then be centralized knowledge, expertise and a network of suppliers and contractors that could react to changes in the threat landscape to produce more units. The organization would also act as a blueprint for other similar organizations to be set up which would further increase production capacity and also use market competition to improve quality and drive down costs.Work with engineers and researchers to give input on how these shelters could fit in a more general plan for responding to a mirror biology crisis. For example, if researchers or risk analysis are developing a plan that relies on manufacturing several such structures quickly at scale, this organization would be able to supply information about the feasibility of various approaches (e.g. would it be possible to use a wide range of sizes and shapes of HEPA filters to create a sufficient seal with the ventilation duct they would be installed in? Or would it be possible to use already-in-use HEPA filters?

There are also some “binary” thresholds in terms of the number of units deployed in a crisis:

Acknowledgements

Input from others have been absolutely essential, this has very much been a team effort. I am just highlight some examples in which the following people have contributed, those examples are far from exhaustive:



Discuss

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镜面生物 避难所 空气过滤 微生物防护 灾难应对
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