Wikipedia:Reference desk/Archives/Computing/2014 May 10

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May 10

Pollution detector ?

I use fans in my windows at night, in summer, to cool the house down. The problem is that my neighbor will light up a cigarette or idle his car in the driveway or pour lighter fluid on his grill, and my house will be filled with pollutants before I can turn my fans off. Is there a "pollution detector" that could flip an electrical switch when pollution is detected, to turn them off ? (I am very skeptical that such a device exists and is reasonably priced, but thought I'd ask on the off chance.) Ideally the device could also close the windows, but I know that's asking too much. Reversing the fans to blow the pollution back out is another thought (although this assumes that there is fresh air somewhere outside the house to replace the air which is blown out).

A device that just sets off an alarm might be of some use, since it could wake me up so I can turn off the fans, rather than me waking to a house full of pollution and choking as I run for the fans. I did at least get my neighbors to agree to stop putting their rotting garbage under my window. StuRat (talk) 03:33, 10 May 2014 (UTC)

Just reverse the fans so they're always blowing outward. They will still cool the house. 70.36.142.114 (talk) 06:09, 10 May 2014 (UTC)

Nope. The air has to be replaced, so air will be sucked in from around the edges of the fans, down chimneys, etc., possibly leading to carbon monoxide poisoning. Pointing all window fans out is a bad idea. But, if I point most of them in, then a few could reverse and blow out without causing a problem. I currently have 9 window fans, 8 of which are in use as I type. StuRat (talk) 13:29, 10 May 2014 (UTC)

Growing up in Houston we often used attic fans. Basically just a fan like 4' x 4' x 1' or so mounted face down behind a grill above the central hallway or some such. One switch on the wall turned it on and the other controlled the direction of airflow (one thing you had to remember was to shut it off and allow it to "spin down" before you reversed the thing!). It was a very effective system, I remember, and seemed to outperform most central AC systems even; in "sucking" mode the thing could make the house quite chilly even on a hot summer day and in the reverse mode, with cracked windows, could clear out any smoke or what have you pretty quickly. I imagine it wouldn't be very expensive to install one either, especially so if you were to do most of the work yourself. Sebastian Garth (talk) 14:21, 10 May 2014 (UTC)

Yes, fans can be far more efficient at cooling a home than A/C, provided cool, dry, unpolluted air is available outside. However, an attic fan would have the same problem, that it would suck in polluted air, until somebody flips the switch, which can take a while, especially if everyone is asleep at the time. You seem to be talking about pollution generated inside the home, by smokers or cooking mishaps, perhaps. StuRat (talk) 14:44, 10 May 2014 (UTC)

You are aware that Houston is quite hot and muggy much of the time, right? The system still works, I assure you. Until you've actually seen one in action you can't really imagine just how effective it can be. And yes, even odors wafting into the house can be summarily evacuated in literally seconds under most conditions (barring say a huge plume of pollution). Maybe not as cold as AC but better air flow in any case...Sebastian Garth (talk) 16:04, 10 May 2014 (UTC)

Sorry, but it's not possible to make your house cooler and less humid using fans, when it's hotter and more humid outside. What they can do, though, is cool off the occupants of the house, by blowing the hot, moist air around them away and replacing it with cooler, dryer house air. You might find that a fan pointing directly at you will be more effective this way, in that 100% of the breeze goes into cooling you, and none goes towards sucking in hot, moist outside air to replace the cooler, dryer air being exhausted. StuRat (talk) 19:12, 10 May 2014 (UTC)

Darn it, in the time it took to write my answer, much of it seems to have become irrelevant now you've added more details. Nine fans, that's a lot. Well, here's my answer anyway, for what it's worth...

Couldn't you put them on a timer so they don't run during likely pollution? I've been looking for good ways to cool during the summer as well, and I've come to the conclusion that fans won't cut it. Opening windows on opposite sides and the doors in between will usually displace more air. The average wind speed in summer is 9 km/h where I live, or 2.5 m/s; assuming that you get the equivalent airflow of that through a one m² (11 ft²) section (in reality the section will be bigger but the speed lower), thats 2.5 m³/sec or 9000 m³/h (5300 cfm). To achieve the same result you 'd need 5 or 6 table fans (12 inch diameter) or a 36 inch whole-house fan like this one.

A whole house fan exhausts to the attic and since hot air rises it gets rid of the hottest air, but with fans in your windows chances are you're pushing out relatively cool air while the hottest air stays inside. And while the wind will move all air in the same direction, your fans could be blowing against the prevailing wind direction and reducing the natural air flow.

I've tried numerous setups with "table fans" over the years, I found blowing air out to be somewhat more efficient than blowing air in, and the best position for the fan was at a distance of some five or six feet from the window, maybe because the air stream pulls additional air along with it, or because the cone of air expands to cover the whole window (the air slows down so the diameter must increase, since it's the same amount of air) so no air is coming in through the same window, which would happen if you put the fan on the window sill (I hung a blanket in front of a second window as a crude measuring device, the angle it made an indication of the amount of air coming in). This works well with a second window facing the same side to let in fresh air, because wind direction wouldn't effect it.

Problem with a fan in front of the window blowing air inside is that in the window plane, you've got a disk through which air is flowing in while around the disk the air is flowing out, so the intake of the fan is surrounded by air coming from inside.

As for pollution detectors, the only affordable thing I can think of is an ionizing smoke detector re-calibrated to a more sensitive setting, but I'm not sure that would work in practice.

I'll probably get me an airco this year, because despite all efforts, every summer the temperature in my room reaches 30°C (86°F). Hardly a surprise, with a flat roof above... Ssscienccce (talk) 14:56, 10 May 2014 (UTC)

Yes, fans work amazingly well, but only when conditions are right. In that respect, they behave like a heat pump. I find blowing air in on the lower floor (where I sleep) and out on the upper floor, works best, as it uses the natural tendency of hot air to rise, and also ensures that the bottom floor will be cooled first, which is where I live. On days in the 70's (F, or course), the fans are all I need. When it hits the 80's, I need to switch to A/C in the afternoon and evening. When it's too hot, even at night, for fans, I must run A/C all night, and that gets expensive. Also, my window A/C units tend to blow mold spores out when I first turn them on, and fans don't do that. Fans can also blow directly on you, and cool that way, but that doesn't cool the house, only you, and the part of you away from the fan, like against the back of the chair, still gets sweaty.

Regarding air slipping back outside around the edges of the fan, I try to only open windows where the fan fits snugly, and I also cut and add sheets of plastic to the corners, to prevent air from slipping back in there. The effect of all this is rather like a wind tunnel. StuRat (talk) 19:07, 10 May 2014 (UTC)

multiple address books outlook 2013

Hi,
I got Outlook 2013, and I cannot create another address book.
When I try, there this message box saying:
"this account or directory already exists and cannot be created twice".
If it is not clear I would like to maintain 2 address books or more.

Does anyone has a solution?
Thanks. — Preceding unsigned comment added by Exx8 (talk • contribs) 15:09, 10 May 2014 (UTC)

Sounds like you may be limited to one address book per account. Have you tried creating another account ? Or perhaps you can do what you want be defining groups within one address book, like "Work", "Friends", and "Relatives". StuRat (talk) 18:55, 10 May 2014 (UTC)

PC-VIRUS - Exploit:Java

Hey, for the last day or two my laptop was strangely slow, so I decided to run my Anti-virus program and discovered two "potential threats". I removed them, obviously. It's certainly not the first time I have picked up harmful malware or whatever one calls it. So it's not really something new.

Both of them were called "Exploit:Java" and something more.. It seems my computer is back to normal speed again after removing them, no lagging, but I'm just wondering; the name/classification that my anti-virus program gave them, does it mean that it exploits my computer through the much used Java-program that probably most people have on their computers? I assume "exploit" means that the malware aims to steal e-mail-addresses, passwords, and usernames that I might have used on the web-sites I frequent... (if so, it might be annoying to me but the thief is probably gonna be left disappointed when finding little of interest)

After removing the viruses I decided to renew my IP-address and erase the "temporary-files", logbook and net-browsing-history, passwords and everything of that sort. I'm not at all an ace on computers, so I'm not sure if it actually does any good. Would there be any point at all in re-installing my Java?

But now that I have removed the viruses, there will be no way for the bas*ard to connect or link or whatever to my computer, right? Especially when I have also renewed my IP-address? Or is it possible that the snake have gotten everything he/she needs to continue "exploiting"? I don't think I have much of value to any of these jerks, but I still want to know, or at least get a decent idea of the situation 109.247.62.59 (talk) 18:30, 10 May 2014 (UTC)

Exploit:Java/whatever appears to be used for files that, if run, would break Java sandbox security by exploiting a bug (the specific bug being the "something more"). This could be used to install malware on your computer if you visited a malicious web site with the browser's Java plugin enabled. But it doesn't tell you anything about what that malware would do once installed, and getting rid of the exploit wouldn't get rid of the malware. I don't even see why the exploit would still be present on your computer, unless it was in the browser's cache. So this doesn't make much sense to me. It might help to have more information: what the "something more" was and where it said it found these threats. -- BenRG (talk) 00:00, 11 May 2014 (UTC)

"Something more" (the rest of the name) was just a bunch of numbers. I don't remember them. I'm thinking my Anti-virus program may have found them in "temp files" (the one that stacks up more and more the more you use internet to visit various sites, don't know how better to explain), but I really don't remember for sure and I may be wrong about the location. But if it wasn't really a virus program, but rather something that was meant to help install malware when and if I entered the wrong site(s), as you say, then surely there's a good chance things never got to a point where I actually picked up anything of the really nasty stuff - and now that I removed the two "exploits" there won't be a way for those types of Java-exploiting bugs to break through ? The real danger, I'm thinking, is enter to net-banks to pay bills or ordering items for delivery over net etc. where there will obviously be sensitive information. Makes me wary. As I said, I don't have any more info on the two exploits, as I have deleted them. 109.247.62.59 (talk) 00:44, 11 May 2014 (UTC)

Here's an analogy (not a perfect one, but good enough). Imagine your antivirus is a police officer patting down all the people (files) in your room (system). The police officer finds some lockpicks (code to make use of a vulnerability in Java) on one of the people, and flags it up to you as potentially suspicious. The officer has no way of knowing whether the person intends graffiti (adware), to squat in your house (viruses), or is actually a locksmith (benign programs). You throw the person out, and you can be reasonably sure that noone left in the room is carrying that kind of lockpick. However, no changes have been made to the lock (Java), so it could still be picked if someone else came in with the right lockpicks (if another file is downloaded which can take advantage of the vulnerability). Your police officer (antivirus) pats down people as they arrive, so he should find any new arrivals carrying lockpicks, but criminals always find new ways to hide things. MChesterMC (talk) 11:01, 12 May 2014 (UTC)

Hehe, I really like your analogy. Good one ;) I'm aware of these things - obviously new stuff that could potentially be harmful can "find its way" to my computer again in the future. All I can do (with help from anit-virus) is to stay vigilant. Thanks 109.247.62.59 (talk) 17:10, 12 May 2014 (UTC)

AVG update

AVG unable to update data base on Vista machine. Any suggestions?--109.151.101.168 (talk) 18:42, 10 May 2014 (UTC)