It is one thing to retrofit a range hood in a single family building with the stove against an outside wall. Conditions will often be more difficult than that. How do you retrofit a range hood into an apartment in a multi-storey building? In a house, what happens if the kitchen is set up to have the cooking surfaces against an inner wall? We have considered suggestions such as tying the range hood ducting into existing exhaust ducting (e.g. a large bathroom fan) or running ducting through a basement under the kitchen.

Have you installed or seen a retrofit such as this and what solutions seem to have worked?

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I might mock up something in my own house as I currently lack a range hood. There is a (too small) 4 inch duct already built into the wall over the range. I could probably use a variable speed in-line fan on that duct and create a hood out of cardboard to test effectiveness. The stove, and the cabinet recess above, is only 21 inches wide - there is no off-the-shelf hood for that arrangement.

My new Dylos is coming in today. I am going to try and calibrate an onion being fried, as I often start a recipe with frying up a diced onion. I will use the Dylos to record the peak on several frying attempts so that I will have a baseline to compare to the same cooking event with a mocked-up range hood. Stay tuned.

So here is my first report (after which I will wait until I have multiple trials). I am trying to set a baseline for frying a single onion plus garlic clove in a cast iron fry pan (8 inch bottom diameter) on an electric burner. The kitchen windows are closed. The Dylos 1100 is about 10 feet away from the stove on the counter. For this trial, the Dylos total count started at 281 counts and peaked at 5100 counts seven minutes later when the onion was soft. I am using this combination as onion and garlic are used in many recipes so I can eat the experiment. Once I find the order of magnitude of the peaks and their variation, I will mock up a range hood and see what if there is a marked difference.

It's possible that the location that you've setup the Dylos will not be actually capture an "accurate" particulate count.  Bear with me a moment.   Since you mentioned multiple different configurations (outside wall,  inside wall, etc).  You might want to make a little mount that allows you to put the Dylos on a (very sturdy) camera tripod -- and then draw a "circle" around that stove at the distance you are interested in... and measure at various points on that perimeter.  It might be that there are areas or pockets in which the airflow away from the stove is still and doesn't move as quickly.   For example our stove is on an outside wall,  ten feet away there are two floor vents (conditioned air from HVAC)  and 20 feet away the return vent that pulls air into the furnace.   The locations of the ducts and the operation (on/off) of your HVAC may influence the measurements you are taking.    I carry with me for experiments some really low cost RH/temp pocket sensors that work really well - they're sold by Thermoworks  #RT819. While these are low cost devices the sensor is reasonable quality and tracks/calibrates to standards reasonably well.    Thermoworks also carries a RH/Temp logger called "Logtag" which can record and upload to a PC data that it captures.  If you are looking at particulate - you might also find that if you are cooking that the changing RH from the water vapor  can also be detected and mapped.

LBNL has done a lot of testing with range hood capture - you might want to look at the research that Dr. Brett Singer (and several others at LBNL) have been involved with..

I have a kitchen vent that goes up about six inches and then out the wall through a damper.  It is amazing how much grease can build up in the duct work.  I would not consider combining with a bathroom duct.   If you're unfortunate enough to have a stove fire - you really don't want the fire following the grease in the duct work up to the Y with a bathroom - and then perhaps moving toward the bathroom.   Without back flow dampers - you might find that lower pressure elsewhare in the residence leads to the kitchen exhaust not following the path you desired.

I would also not run the kitchen vent down and through a basement - think condensing the grease in the ducts.  If the duct goes up through cabinet and ceiling and out - you have the advantage of using the heat to help keeping the greases and moisture moving... move toward the basement - and that downward motion means you're probably loosing energy (from the hot fumes) in the pipe... speeding up the condensation.   You can see problems like this from clothes dryers that sometimes go down through the floor - then out toward the wall and up just above the sill.   Moisture is captured and the ducts have problems collecting lint and staying clean.   You'd likely have the same thing with grease and moisture from the kitchen.  Anything that has an opportunity to :"take energy" out of the exhaust fumes - means condensation.

Grease filters DO NOT capture ALL the grease,  they only capture a small amount of the worst grease.   I can see that in even that short duct work in my kitchen.  Charcoal hood filters DO NOT solve the problem -- unless you are willing to replace them frequently -- every few weeks if you cook a lot.  (Common mistake passive house people some times get caught by... thinking charcoal filters will capture all the bad stuff and last for months or years...)

The beauty of a duct running in an unfinished basement is that you can put a clean-out/inspection cover at the bottom of the vertical run and check it ever so often.

It's amazing to see how much junk are in some types of ducts.  I doubt anyone except the original owners would every think of checking and cleaning out the duct.  Many would not understand what its for - and worse someone else may see it as an opportunity to tie additional duct work into it.

Something also to consider is that an end-cap implies either a T,  or a nice Y transition that will have some air swirling around at the junction.  The swirling air will loose energy,  which means cooling down faster,  depositing grease and moisture faster.

I've done quite a bit of field work looking at clothes dryers.  One of the first things we learned to check was the clothes dryer ducts.   I've seen multiple ducts that were in crawl spaces and disconnected... with an crawl space coated in lint!!   I had one dryer duct that had THREE birds nests in it... causing the moisture and dryer products to back up into the house... The dryer was natural gas!

In my house - when I replaced the original stove/oven and hood,  I discovered that the contractor had vented the exhaust into outside wall, NO METAL DUCT,  and a simple flapper on that outside wall.   I needed to open up the whole wall to clean up the mess and properly install a simple duct to the outside.

I fixed that duct in the wall by going to the equivalent of a flat (oval) duct that had the same area as a round duct.  Rounder/oval smoother inside with fewer square corners cuts down the air turbulence.

I've seen too many installations in which somebody tried to do clever tricks to save bucks.  I've yet to find an owner that knew how to clean dryer or kitchen hood vent ducts.   If you do run it into a basement label it, the end cap and how to clean it.  

OK, I did five trials of approximately the same set-up. Each time the onions were ready and taken off the burner (or squelched with canned tomatoes) 8 minutes following the start of heating. Initial Dylos total readings ranged from 72 to 281. Peak Dylos total readings occurred at the 8 minute mark and ranged from 977 to 5100. That is enough of a bump that we should see a difference with decent range hood capture. Now all I have to do is buy a fan, assemble the ducting, and construct a hood. This will take a while.

If you have a microwave oven in the same approximate area - repeat some of the tests with the microwave (using covered microwave save pans)  I think you see numbers that are in the same range.  

I suspect you could see some of the same results if you boil water over a burner on the stove.  One of the questions need to be asked is if the particulates you are seeing are harmful  or not.

The particulate counter can determine if the particulate it is seeing is bad or okay,  it just saw a speckle of light in the path of a laser beam.  Steam creates speckles quite nicely.  Commercial light shows often use smoke generators using a glycerin agent to make the fog for the beams to be easier to spot.

You might be able to help identify the products in the air... if you can collect air samples ... draw the air through a beaker that has a know amount of de-ionized water in it... then have someone check what's been captured in the water...  


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