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Questions tagged [air-quality]

Questions about the control, measurement and regulation of air contaminants impacting public health and/or visibility. Do not use this tag for questions specific to greenhouse gases and climate impact.

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How was Volkswagen able to trick the lab pollution test?

The recent Volkswagen pollution test cheating scandal has shocked many people with its widespread extent as well as how it was hidden for so many years. Last year, the International Council on Clean Transportation (ICCT) in Washington DC…
March Ho
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How long does it take for dust to settle out of the air?

In order to make this a manageable question, let's add a few simplifications. The dust particles can be well described as uniform spheres of radius $R$ and density $\rho$. The space is enclosed and there is no bulk flow, i.e the air is still in…
Chris Mueller
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Is there a more active passive technique for removing humidity from the air besides salt blocks?

We can get really humid days sometimes. Recently I was digging around in boxes and found some old mineral specimens, and I set out a few of the salt crystal rocks. I soon found that they had pools of water accumulating underneath them, which…
New Alexandria
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Why did Volkswagen use special software ONLY during emissions testing?

As we all know, Volkswagen is in the middle of a scandal centered on its use of special software to lower tailpipe emissions during standard emission testing protocols. What I don't understand is why this software needed to be switched off in other…
Gremlin
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How do cyclonic vacuum cleaners maintain collection efficiency with constant motion and changes in orientation?

Anyone used to doing housework has probably noticed that vacuum cleaners come in both "bagged" and "bagless" varieties. If you're of a certain age, you may have noticed when these "bagless" vacuums appeared back in the 1990s. Though I didn't…
Air
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Which component of vehicle tailpipe emissions has the greatest social cost?

Emissions Emissions from vehicles have an associated social cost for everyone. We hear a lot about CO2, but CO2 is not the only thing that comes out of a tailpipe. From Wikipedia, emissions components of petrol and diesel engines…
hazzey
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Do high speed trains use ventilation and filtration systems similar to aircraft?

This article discusses the ventilation and filtration in aircraft: Ventilation rates provide a total change of air 20 to 30 times per hour. Most modern aircraft have recirculation systems, which recycle up to 50% of cabin air. The recirculated…
sba222
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EU EN standard 1822 vs US HEPA filters

There's a EU EN standard 1822 for air filters that has seen several iterations. The pre-2009 versions of EN 1822 (which seems to have come out in 1998) were pretty confusing as they allowed poorer filters to be labeled as H or HEPA; e.g. a "HEPA…
Fizz
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What would happen if the air conditioning failed in a skyscraper for an extended period?

I'm writing some fiction which involves the AC in a modern glass curtain skyscraper (50-80 floors?) in an American city failing for a period of weeks, maybe even for up to two months. Could anybody attempt to predict the type of conditions which one…
Reverend Speed
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How to select a smartphone IR camera for VOC monitoring

I am currently working on a problem involving volatile organic compounds (VOC) source monitoring on some oil and gas transportation environment. I think using infrared (IR) cameras could be a straightforward approach. The core idea is that…
Talles1988
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How to filter outside air during wildfire to safe breathable level?

I've had an experience of having outside air heavily polluted by wildfire smoke, and now I'm reading up on the wildfire happening in Southeast Asia. When the air outside got too polluted to breathe, I covered a plain old fan with a wet cloth and…
user1306322
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Applications of CO$_2$ sensors

I am working on a project where I am creating a new type of CO2 sensor. (I can't give details on the functionalities). I am looking for applications to showcase the capabilities and the usefulness of my sensor. Description: The size of the sensor…
Anwar Elhadad
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Is this an isenthalpic process?

My professor told us that If we spray water in dry air the process is on an Isenthalpic line of the Mollier diagram. Is it always true? if yes, can you explain me why?
SimoBartz
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Should we use exhaust fans during wildfire smoke?

We have exhaust fans in our baths, kitchen and master closets. There are wildfires with a lot of smoke. Our house has HVAC and was recently remodeled. Should we use exhaust fans?
Cynthia Volpi
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HVAC Bag Filter Backwash

I need to install a replacement air handler in a facility that has an area where a large volume of particulates are in the air. Unfortunately, the previous designer tried to get away with the cheapest design possible and just put in pleated filters…
Secundus
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