[SOLVED] portable a/c for wildfire smoke?

coyote2

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Oct 29, 2009
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A major reason I need an air conditioner is to survive California's extreme wildfire seasons.

I need a portable a/c and I need to vent it's hoses through a sliding glass door (there are third-party kits for the standard hose sizes).

I have separate air filters, but I want a dual-hose model to avoid having negative pressure pull in toxic air through cracks.

It's easy to find such models...

But I also need it to have a HEPA filter to deal with wildfire smoke drawn in through the intake hose.
(As I understand it, Activated Carbon filters don't filter smoke particles as well as HEPA. And I've read that it's important to use a HEPA filter supported by the unit, because they restrict airflow. I already have separate HEPA filters.)

The only unit my search turned up that meet all these criteria is https://www.whynter.com/product/arc-147wf/ but it's not available for sale anywhere.

My Berkeley, California rental apartment is 450 square feet.
 
Last edited:

velocityg4

Illustrious
AC

I think you have a general misunderstanding of how these AC units normally function. The air inlet duct is for the condenser. Air from outside is drawn through the condenser and exhausted the exhaust vent. This is to dump the heat which builds up in the condenser from compressing the refrigerant.

The cooling part is the evaporator. Air from inside the house is drawn through the evaporator and vented back into the house.

Unless this is some fancy model with a heat exchanger or doubles as a fresh air intake. The evaporator and condenser sections are isolated from eachother. Air from outside never goes into your house. Excepting possible some small leakage if it isn't totally sealed. The air only goes from outside through the condenser then back outside. It would be totally inefficient to do otherwise.

Here's a very rough diagram of what I'm talking about.
View: https://imgur.com/a/g8RVdVy


The main reason you want a portable with two ducts is so the air circulates through the condenser continuously. These are far more energy efficient and effective than a single duct unit. I'm not even sure how a single duct unit manages to work.

HEPA filter

These are extremely fine filters. They are equivalent to a MERV rating of 17-20. It's doubtful you'll find these in any portable AC unit. They require considerably more powerful fans/blowers with a high static pressure than most units can handle. Heck most home furnaces can't handle this either. They crap out at around MERV 12/13. Hospitals and labs use much more powerful commercial HVAC systems which can handle the restricted air flow.

You'll want a separate room air purifier for this. Large units move a lot more air. If you're dealing with a lot of smoke you'll want this. As they typically have multiple filter stages. These stages help the HEPA filter last longer. As they get the larger contaminants. Reducing what the expensive HEPA filter deals with. A good unit will have a pre-filter, carbon filter and HEPA filter. They are noisy as the HEPA filter needs a powerful blower to move air through it.

Smoke

I assume you are concerned about the smell and irritation from particles. A good air purifier with hepa filtration will handle this pretty well. How well depends on the capabilities of the system. There'll always be some odor as your apartment isn't designed to be fully sealed with fresh air coming through a heat exchanger. Where you'd be able to filter all incoming air.

Just note the filters only good for particulates and odors. You also want it to have a carbon/charcoal filter stage as this handles some other chemicals in the smoke and absorbs some of the odors. Neither the HEPA or carbon filter can do everything. That's why you want stages.

Water

Unless you want to be dumping water frequently. You need to run a hose from the AC outside. Put the AC on a little platform so it's higher than the hose. End those hose a few feet away from your door outside if you can. You don't want to attract bugs anymore than you have to.

Sealing

Seal the unit at the door or window the inlet/outlet duct is. This will reduce energy waste and insects getting in. You'll also notice a partially open window or sliding glass door also has a gap between panes. Fill the gap with foam weather stripping. Really just look all around the door or window for any opening air or bugs can get through and seal them. Wedge something in the top and bottom of the door to make it so no one can open it. You can get door security bars for this.

Humidifier

If you are in a part of CA with dry air. The AC is just going to make this worse. Really dry air can cause all sorts of sinus issues. You may want a humidifier to get some moisture back into your air.
 
Last edited:
Reactions: Mandark and coyote2

Ralston18

Titan
Moderator
If your apartment already has an air conditioning unit then it probably has a filter in that air conditioning unit.

Likely the cheapest and least effective filter possible as deemed applicable by "management".

Check the AC unit. Size the filter and replace it with a HEPA filter that meets your requirements.

I have family in Southwestern Oregon and dealing with forest fire smoke is a continuing issue.

Limiting or otherwise controlling exposures to smoke and accompanying toxins is problematic at best.

Not a doctor (full disclosure); however, I will still suggest that you discuss "toxic air" and other similar issues with a health care professional.

Could be that your worries are "no worries".

If I am wrong about that then listen to medical advice.
 

coyote2

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Oct 29, 2009
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My apt. does not already have any a/c.
And no portable a/c I can find supports a HEPA (that's the purpose of my post, I'm hoping to hear of one that supports the restriction of airflow that HEPA creates).

After living through years of wildfire seasons, I know it is a problem I need to solve.
 

Ralston18

Titan
Moderator

velocityg4

Illustrious
AC

I think you have a general misunderstanding of how these AC units normally function. The air inlet duct is for the condenser. Air from outside is drawn through the condenser and exhausted the exhaust vent. This is to dump the heat which builds up in the condenser from compressing the refrigerant.

The cooling part is the evaporator. Air from inside the house is drawn through the evaporator and vented back into the house.

Unless this is some fancy model with a heat exchanger or doubles as a fresh air intake. The evaporator and condenser sections are isolated from eachother. Air from outside never goes into your house. Excepting possible some small leakage if it isn't totally sealed. The air only goes from outside through the condenser then back outside. It would be totally inefficient to do otherwise.

Here's a very rough diagram of what I'm talking about.
View: https://imgur.com/a/g8RVdVy


The main reason you want a portable with two ducts is so the air circulates through the condenser continuously. These are far more energy efficient and effective than a single duct unit. I'm not even sure how a single duct unit manages to work.

HEPA filter

These are extremely fine filters. They are equivalent to a MERV rating of 17-20. It's doubtful you'll find these in any portable AC unit. They require considerably more powerful fans/blowers with a high static pressure than most units can handle. Heck most home furnaces can't handle this either. They crap out at around MERV 12/13. Hospitals and labs use much more powerful commercial HVAC systems which can handle the restricted air flow.

You'll want a separate room air purifier for this. Large units move a lot more air. If you're dealing with a lot of smoke you'll want this. As they typically have multiple filter stages. These stages help the HEPA filter last longer. As they get the larger contaminants. Reducing what the expensive HEPA filter deals with. A good unit will have a pre-filter, carbon filter and HEPA filter. They are noisy as the HEPA filter needs a powerful blower to move air through it.

Smoke

I assume you are concerned about the smell and irritation from particles. A good air purifier with hepa filtration will handle this pretty well. How well depends on the capabilities of the system. There'll always be some odor as your apartment isn't designed to be fully sealed with fresh air coming through a heat exchanger. Where you'd be able to filter all incoming air.

Just note the filters only good for particulates and odors. You also want it to have a carbon/charcoal filter stage as this handles some other chemicals in the smoke and absorbs some of the odors. Neither the HEPA or carbon filter can do everything. That's why you want stages.

Water

Unless you want to be dumping water frequently. You need to run a hose from the AC outside. Put the AC on a little platform so it's higher than the hose. End those hose a few feet away from your door outside if you can. You don't want to attract bugs anymore than you have to.

Sealing

Seal the unit at the door or window the inlet/outlet duct is. This will reduce energy waste and insects getting in. You'll also notice a partially open window or sliding glass door also has a gap between panes. Fill the gap with foam weather stripping. Really just look all around the door or window for any opening air or bugs can get through and seal them. Wedge something in the top and bottom of the door to make it so no one can open it. You can get door security bars for this.

Humidifier

If you are in a part of CA with dry air. The AC is just going to make this worse. Really dry air can cause all sorts of sinus issues. You may want a humidifier to get some moisture back into your air.
 
Last edited:
Reactions: Mandark and coyote2

coyote2

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Thank you very very much for the priceless info, @velocityg4!

I admit I'm quite confused now, since I've read in reviews of portable a/c units by people dealing with wildfire smoke in California, that so much smoke comes in from the outside that multiple separate HEPA filter units can't keep up.

In addition to one HQ filter with HEPA and Activated Carbon, I have many DIY MERV 12/13 filters, and they do a good job on the smoke.

Raising the portable for drainage is a great tip, thank you very much for that too!

I've read a lot for weeks, but your post was the best most thorough info I've seen!

I think it's time for me to contact some portable a/c resellers (that sell a range of brands) and get their advice on which to buy to deal with our horrific smoke periods.
 

coyote2

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Oct 29, 2009
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@Ralston18
Thank you very much for your reply!

I know that typically people come here with questions they have put no time into themselves. But I'd already googled for many dozens of hours.

"AC is one thing. HEPA is another."

And that is my problem; I was trying to find an a/c with both, and it's seemed there are none available. The a/c units only have dust filters.

If only the creators of web pages that our searches pulled up had worked as hard; it invariably turned out that even when they said a portable a/c had a HEPA filter, it actually didn't.
 

coyote2

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Oct 29, 2009
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The only unit my search turned up that meet all these criteria is https://www.whynter.com/product/arc-147wf/ but it's not available for sale anywhere.
I just heard back from the manufacturer Whynter; the reason I can't find their ARC-147WF is that it isn't out yet.

But maybe I don't need to wait based upon the education I got velocityg4 about outside air not coming inside. I'm gonna talk to a reseller(s) to get clarity on my best option.
 

velocityg4

Illustrious
Thank you very very much for the priceless info, @velocityg4!

I admit I'm quite confused now, since I've read in reviews of portable a/c units by people dealing with wildfire smoke in California, that so much smoke comes in from the outside that multiple separate HEPA filter units can't keep up.

In addition to one HQ filter with HEPA and Activated Carbon, I have many DIY MERV 12/13 filters, and they do a good job on the smoke.

Raising the portable for drainage is a great tip, thank you very much for that too!

I've read a lot for weeks, but your post was the best most thorough info I've seen!

I think it's time for me to contact some portable a/c resellers (that sell a range of brands) and get their advice on which to buy to deal with our horrific smoke periods.
Those units have horrible inserts for sealing windows. If people are just using those. Which I expect most do. That would be a problem. I use window mounted units which replaced my dead central AC. Just the inserts allowed in tons of hot and humid air. I took the time to insulate and seal them. No issues anymore. It also improves energy efficiency as you don't have huge gaping seams.

Unless the unit is a fancier one designed to blow air into the house in an intake fan mode. Any outside air infiltration should be minimal. The barrier separating chambers may not be fully sealed (my window unit is fully sealed from the factory). So a little may get through that if it isn't. Along with imperfections in the duct joints. Maybe when you turn it on. Check the duct joints for any leakage and tape them with duct tape if needed. You might also wrap them with fiberglass duct insulation to reduce any thermal transfer.

AC window mount. Sealed with aluminum duct tape around perimeter. Using Owens Corning Foamular 150 for insulation. You'll notice one area above the AC not taped. That's just because I put weather stripping there.

View: https://imgur.com/JWP0Fvw


This is the gap between window panes. It's stuffed with a 1 1/2 inch expandable foam weather strip.

View: https://imgur.com/a/oDuuNxP


I will add that when my neighbors burn leaves. I don't smell anything indoors. Besides sealing the window units. All the molding around my windows are caulked. Along with any other joints in my window frames.
 

coyote2

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@velocityg4
I talked to people at both Sylvane and Whytner, and they said you're right, that outside air is only used to cool the condenser, not blown inside!

(As you said, they said one should expect some 'leakage' though.)

OMG I'm so happy! (Without a/c it's gotten so hot in my apt. I've had to open windows despite the hazardous air.)

I'm also disappointed in the misleading info out there. For example, before I called Sylvane, I read this on CNET:
"Dual-hose portable air conditioners...don't use the air inside your home. Instead, they pull fresh air from the outside through that hose attached to the window. That's the air the portable air conditioner will cool and then circulate through the room.".

Wow, that was unhelpfully misleading for me and my extreme wildfire smoke months.

The agent at Whytner guessed that their new ARC-147WF (w/HEPA) might be out about Sept 1, so I may hold off until then. (Both fire season and the hottest part of summer here in Berkeley usually start after that.)

Thank you very much for the advice on sealing. I had read up on it, but I've never even heard of aluminum duct tape. Maybe in addition to foam strips, I will re-apply duct tape every heatwave on the Sliding Glass Door Kit I get.
 

velocityg4

Illustrious
@velocityg4
I talked to people at both Sylvane and Whytner, and they said you're right, that outside air is only used to cool the condenser, not blown inside!

(As you said, they said one should expect some 'leakage' though.)

OMG I'm so happy! (Without a/c it's gotten so hot in my apt. I've had to open windows despite the hazardous air.)

I'm also disappointed in the misleading info out there. For example, before I called Sylvane, I read this on CNET:
"Dual-hose portable air conditioners...don't use the air inside your home. Instead, they pull fresh air from the outside through that hose attached to the window. That's the air the portable air conditioner will cool and then circulate through the room.".

Wow, that was unhelpfully misleading for me and my extreme wildfire smoke months.

The agent at Whytner guessed that their new ARC-147WF (w/HEPA) might be out about Sept 1, so I may hold off until then. (Both fire season and the hottest part of summer here in Berkeley usually start after that.)

Thank you very much for the advice on sealing. I had read up on it, but I've never even heard of aluminum duct tape. Maybe in addition to foam strips, I will re-apply duct tape every heatwave on the Sliding Glass Door Kit I get.
Oh my god! That article is so horrible it's funny. I didn't read all of it. I just glimpsed and the first thing I saw was.

"Most units include a water reservoir to help dehumidify the air it is circulating."

That's just laughable. It's not to help dehumidify the air. Air passing over cold fins will condense like on a glass of ice water. If you don't have a way to catch it, reservoir, or drain it, a hose. You'd have water all over your floor.

Did they even research anything? It seems like they just looked at a few units on home depot's website. Saw some specs. Then made assumptions about what everything does.
 

coyote2

Distinguished
Oct 29, 2009
113
5
18,585
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Oh my god! That article is so horrible it's funny. I didn't read all of it. I just glimpsed and the first thing I saw was.

"Most units include a water reservoir to help dehumidify the air it is circulating."

That's just laughable. It's not to help dehumidify the air. Air passing over cold fins will condense like on a glass of ice water. If you don't have a way to catch it, reservoir, or drain it, a hose. You'd have water all over your floor.

Did they even research anything? It seems like they just looked at a few units on home depot's website. Saw some specs. Then made assumptions about what everything does.
Now that I look at the Comments on it, I'm happy to see it was appropriately attacked.
 

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