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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48
votes
2answers
10k views

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 ...
12
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2answers
9k views

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 ...
6
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5answers
2k views

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 ...
5
votes
0answers
128 views

Why did Volkswagen use special software ONLY during emissions testing? [duplicate]

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 ...
4
votes
1answer
517 views

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 ...
4
votes
2answers
1k views

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 ...
3
votes
0answers
34 views

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 ...
3
votes
1answer
2k views

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 ...
2
votes
0answers
67 views

How to select a smartphone IR camera for VOC monitoring [closed]

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 ...
1
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3answers
16k views

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 ...
1
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2answers
91 views

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?
1
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3answers
47 views

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 ...
1
vote
1answer
39 views

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?
1
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1answer
1k views

What is the shelf life of HEPA filters?

I was not sure on which site to ask this question, but I guess Engineering might do well from the aspect of matter. I am wondering, what is the shelf life of a HEPA filter, can I just buy a few of ...
0
votes
1answer
30 views

Single Split Air Conditioner & Supply/Exhaust Fan

First Question Does single split AC (the type with evaporator indoor and compressor outdoor) vent or exhaust air outside and thereby create negative air pressure in the room? Reason being I am ...
0
votes
0answers
31 views

How to purify/treat air smell produced by a kitchen?

Ignore the ugly look. Sometimes I cooked food with very strong smell. That smell sometimes is not expected by many neighbors, they protested. Rather than to use exhaust fan, I considered to install ...