Depends on your vehicle's design, you can simply get a cylindrical shaped filter and duct tape that onto your intake opening (although most passenger cars are too cramped in engine compartment to do this).

Or you can just put a sock on it, offroaders do this after their filter gets waterlogged and must be removed.

I was thinking of a fairly large box, too big to stuff into any engine compartment I'm familiar with. I'm thinking a standard medium mover's box (18x18x16) And cutting off the 18x18 side so you have 2.25 square feet of open area. More cross-section area equates to less air flow per unit area and less chance the caked ash will be held onto the filter by the air flow.

The intake on my truck is a rubber hose that is tucked in front of the wheel well. The when well is plastic so cutting a hole to allow a hose to pass should be an issue. The hose would come out the top of the wheel well and up onto the hood where the large box filter would be mounted on blocks filter side down. Duct tape and cargo straps should hold it down well enough.

Made out of plywood and with a little streamlining the box should ride at any reasonable speed. A cardboard box would be more delicate and might require you to drive slower. Then again with ash limiting visibility driving slow might be wise.

Filterwise I'm thinking pantyhose material might be better than a furnace filter. Furnace filters are 'depth' filters and tend to trap the crud they filter out. That's good for a house where you simply replace them but in this roll you want something that will drop the ash if you give it a whack.

I would try two layers of pantyhose material and drop to one if it seemed too tight.

I would think that doubling the filter area would have no other effect than doubling that time / distance - every 4th mile or 4th mile. No doubt a big improvement, but perhaps not the one you were hoping for.


I can try to poke around and see if I can hunt down some Icelanders and ask them. They're off season right now, but let's see who I can find.

In Operation Desert Storm, I see to remember that the fine sand was clogging tank/vehicle air filters and that the field expedient remedy was to stretch panty hose over the air filters.

> I guess the idea was that the inside of the car is cleaner than the outside air.

I'll say this isn't so.

Louise and I camp at Burning Man every year, and the playa surface is a very fine powder. Maybe finer than volcanic ash, maybe not. A sample video:
http://www.flickr.com/photos/civex/2831873456/
The worst dust storm we've been in was when the visibility was four feet; when visibility is four feet, you can't see the ground you're standing on.

The interiors of every vehicle at Burning Man is covered in dust. Worse, all the air intakes are full. When you start your car/truck/whatever, you get a huge blast of powder out the A/C vents that lasts a long time, further coating all the front seats in another layer of dust.

The seals on the doors don't protect against intrusion of the powder, the filters (if any there be) on your A/C intakes don't protect. I would not expect the interior of any vehicles in a Mt. St. Helens type eruption to be any cleaner than the outside air, _especially_ if you have a window cracked open and "sealed" against air.

Last week I turned on the air conditioner on our van for the first time this season, and I got a whiff of playa powder out the vents. shrug - fortunately it's a reminder of great adventures, so it's not a problem. The van was on the playa last American Labor Day.

I would suggest you're better off changing the air filter frequently. I'm not sure how long one would expect ash-falls to continue, but clogging the air filter is likely to take some time. I'd start with some research on that answer before doing anything else. If heavy ash were a concern for me, I'd have a couple of air filters in the trunk.

I'd say put a higher capacity filter in if you're that worried about it, but basically just follow the advice of cleaning the filter. Ultimately, I'd much rather damage my engine than have it suck air from inside the passenger compartment - if the interior air is any cleaner than the exterior air I just assume I breath that clean air and let my engine die a little quicker.

You can also wrap a new flannel shirt around your air filter and run til it clogs up w/ash. Then shake out the flannel cloth (downwind of your car), rewrap your filter and continue til it clogs, and repeat til you clear the ash cloud.

Youy want a new piece of flannel in order the catch the most particles and save your filter to the maximum distance/mileage.

I'm hoping that I never have to deal with it. The people who have done so said it's really nasty.

Thank you for all the input.

Sue