本系列播客节选自为期两天的“建筑科学基础”课程，由建筑科学公司的Joe Lstiburek博士和John Straube博士教授。

上周，约翰博士讨论了湿度及其对建筑物的损害。本周，乔博士解释了他最喜欢的评估室内空气质量的方法，以及它为什么有效。他还指出，空气污染物通常是建筑材料被水、热、紫外线和臭氧分解的症状。

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实用空气质量评价

我们要做四个p:人，污染物，路径，压力。这是一种观察室内空气质量的方法，这是一种完全不同于传统工业卫生团体对室内空气质量的看法，传统工业卫生团体对室内空气质量的看法是基于污染物的浓度和稀释。这种方法完全正确，完全准确，但完全没用。我要提出的方法不是完全准确的，不是完全准确的，但非常有用。所以，作为一个工程师，这是近似正确的，但不是精确或严格正确的。所以它会让你用很少的努力就能理解发生了什么;一旦你弄清楚了整体情况，你就可以转向传统的工业卫生方法。

它是如何工作的

好吧。这是基于什么?如果有人在这里，而污染物在那里，就不会有问题，因为人和污染物不在同一个地方。你需要一种方法让污染物到达人体;所以你需要一种联系。你需要一条路径。如果有人在这里，污染物在这里，你有一条路径，你就有问题了。好吧，你还没有——你仍然需要一些东西把污染物推到人类的道路上。你需要压力。所以要产生问题，你需要四个因素:人，污染物，路径，压力。

许多不同的人及污染物

人的问题就在于他们是人!没有两个人是相同的，所以很难从人们那里得到一致或相同的反应。有些人对同样的暴露比其他人更敏感。我是一个非常敏感的人，你知道，即使是对适度的接触，我的反应也很奇怪。你知道吗，少量的酒精就会让我做出非常非常奇怪的事情。不管怎样，人们在相同的环境下不会有相同的行为。所以很难对暴露提出建议，因为，你要如何选择哪一群人，或者你要和什么样的人打交道?就污染物而言，有成千上万的污染物可以处理!你会选哪一个?如果你只是试图测量污染物，你会破产的。 The problem with pollutant measurement technology is that we don’t have the ability to go into a space and measure the pollutants in the space. Now I’m going to be very careful about what I’ve just said. If you go into a space, we don’t have the technology to measure the pollutants in the space. You don’t go into a space and ask: “what’s in the air in this space?” You go into a space and you ask: “is this in the space? or this in the space? Or is this in the space? You’ve got a million choices to ask about. So when somebody says: “We’ve tested the air in this space, and we didn’t find anything.” No, what they’re really saying is, “What we tested for we didn’t find within our limits of accuracy of the test procedure that we used.” That’s very, very different from saying, “There’s nothing wrong with the air.” Just means what we tested for, we didn’t find within the limits of the test.

不要从空气测试开始

那你怎么知道要检测什么?在你已经理解问题之前，你不应该进行测试。所以，这就是为什么所有真正了解室内空气质量的人，比如美国环保署和亚特兰大的疾病控制中心，说你应该做的最后一件事是通过空气测试来开始室内空气质量调查。因为你用在测试上的钱都不能用来解决问题。空气测试总是会在空气中发现东西，你只是不知道它意味着什么。还有更糟的。如果你发现空气中有东西你必须问自己，它是好还是坏?更重要的是，它从何而来?我们不知道它是好是坏，因为很少有污染物已知剂量/反应关系，所以我们可以设定可接受或不可接受的限制。所以很难测量空气中的某种物质，然后说，“这实际上很糟糕，但如果它低于这个浓度就会很好。” We can only do that with very few things. Usually it’s stuff that people don’t manufacture, make, or distribute. So we have really, really good standards for radon. Why? Nobody makes it. Who are you going to sue, God? Right? So let’s say you find something in the air. Where the hell does it come from? Well, that’s pretty fundamental, or pretty important.

污染物通常来自损坏的材料

所以我要说的是，忘了它吧。大多数污染物来自于非常热的东西，或非常潮湿的东西，或暴露在紫外线或臭氧下。我们称之为损伤函数。当破坏功能作用于材料时，它们会破坏材料。这就是为什么我们称它们为损伤函数。损伤的后果之一就是物质会散架。当它分解时，分解的颗粒通常是污染物，以气体和颗粒的形式存在。所以你让材料损伤函数,你打破产品可以被视为污染物气体和粒子和粒子的形式非常小,他们有一个非常微小的空气动力学直径可以进入空气,并在空中运输固体形态。

最大的来源是什么?

那么你的大楼里哪个部分最热，最潮湿，暴露在紫外线和臭氧下最多?它的屋顶。典型的屋顶是什么样的?黑色的三元乙丙橡胶薄膜。7月，你站在黑色三元乙丙橡胶薄膜屋顶上。温度是多少?180度。所以你走到屋顶上，站在那里，然后你去(吸气)——你闻到了什么?屋顶!屋顶释放出大量的挥发性有机化合物。 If you take your hand and you rub it on the top of the roof it’ll actually fall apart in your hand. If those particles get into the air we have an aerosol. So you can actually sense — feel with your own nose because your nose is actually more accurate for detecting chemicals than a gas chromatograph — and you can actually smell the roof breaking down while you’re on it. Which is why it’s always a good idea to put you’re building’s fresh air intake up on the roof. Because you then actually hoover up the VOCs and eject them right into the breathing zone of the occupied space.

污染物是症状，而不是问题

这里的模具工人是谁?这里有几个做模具的。我们学到的是，你不会去寻找霉菌，因为你总是会在空气中找到霉菌。你要找的是潮湿的地方，因为那是霉菌的来源。所以你通过寻找水来寻找霉菌。对吧?所以你搜索VOCs不是通过寻找VOCs;你通过寻找会释放VOCs的热的东西来搜索VOCs。所以你通过寻找热的，潮湿的，暴露在紫外线下的，或臭氧下的东西来寻找污染物。然后问你自己，这些东西是否通过路径和压力关系与被占用空间的呼吸区相连? I only sample after I know what’s going on, in order to shut up people that don’t know what’s going on. So you don’t look for pollutants, you look for the hot spot, the wet spot, the spot that’s exposed to ultraviolet light and ozone and work backwards via a pollutant, pressure, and pathway relationship. So you do an indoor air quality investigation by thinking in two dimensions at the same time. On one axis is what? People, pollutant, path, pressure. On the other axis is hot, wet, UV. Now, there’s ozone in there, but the first three damage functions are in order of magnitude more significant than the fourth one. So the really, really important ones are hot, wet, UV; ozone is kind of important, but it’s not in the same league as the other one. Why even mention it? Because it’s not insignificant. In other words it’s not the big three, but it can cause you some grief. Are you with me on this?

这些影响的破坏性有多大?

现在，通过自身的这些影响每一个是烦人。两个或三个它们共同作用是非常非常糟糕。我们认为这些作为指数和协同。指数意味着每本身的影响会非常，非常，非常糟糕，但也不是一个线性增加，但一个真正的斜坡增加。因此，我们知道随着温度，每十度上升开尔文在材料​​加倍抽气速率。这十八个华氏度。所以，你加倍每18度的材料的捣蛋。使用乔数学这大约需要多少？二十。所以，每二十度增加你加倍的脱气。 Now, it doesn’t take very long to have a factor of four. That would be how many degrees? Forty. Cause it’s two by two, so the first twenty degrees doubles it, the second twenty degrees doubles the double. So that would be four. See you want your salary to be increasing exponentially, not linearly. Right? Ok. Now the same thing with humidity. It turns out as you double vapor pressure, you basically double off-gassing. And that’s approximately eighteen percent relative humidity. That’s purely by chance. They’re not connected, the eighteen and eighteen — it just happened serendipitously … accidentally … I can’t even frickin’ pronounce it. Alright. Now the same thing with UV light. Every ten percent increase in UV light results in the doubling of the factors. Now when any two of them are acting together, they’re not additive affects, they’re multiplicative affects, so if you really what to trash something, make it hot, make it wet, and expose it to sunlight. And then zap it with a little bit of ozone.

人们为什么要关心呢?

这是对人类，而不仅仅是材料的同样的事情。这是真的。如果你想住时间长了，你去一些地方，它的冰冷，它的干，你保护自己免受紫外线，你离市区远点，因为市区有哪些？臭氧！你吃坚果和浆果。所以，你会住了很长时间，但你会觉得苦不堪言，祝你死了。那么，是退休最差的地方？佛罗里达！因为你也要去那有什么地方？热，潮湿，湿度，这是一个市区。 So you’re going to frickin’ die. Alright, let’s go to hospitals. The worst thing to do if you’re sick is to be in a humidified space. The dryer it is, the healthier it is. So why do we humidify hospitals? Cause they’re filled with explosive gasses and we don’t want them to blow up. That’s very unhealthy. Unfortunately, you get lots of mold and bacterial growth and that’s really bad, cause if you’re sick, your immune system is weak, and you’re exposed to these opportunistic pathogens. So the most dangerous place to be if you’re sick is in a humidified hospital. It’s part of the new health care system. Alright. People, pollutants, path, pressure. Cause there’s always going to be a pathway, and there’s always going to be pressures. You can never get rid of all the holes, you can just get rid of the big holes.