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A Clean-Air Kitchen Checklist

It’s clear from the amount of money and size of kitchens nowadays that the kitchen is where people spend a lot of time.  Big islands, comfortable chairs and features like coffee bars and wine coolers make it easy to stay and chat while the host cooks up a delicious meal.  The problem is that some things get overlooked in kitchen design and maintenance, so that hidden appliances may be making your air dirtier than your guests would expect! 

Kitchen exhaust vent

We’ve previously posted about how cooking and baking can raise fine particulates and VOCs in your kitchen to levels of a polluted city.  The best defense against spreading them to the rest of the home and breathing them in is to use your kitchen exhaust vent.  The problem is that the exhaust vent filter is often overlooked, and a clogged filter strains the vent motor and can throw particles right back into your kitchen.  Here’s where it’s important to a) check whether your vent is recirculating or exhausting to the outside, and b) clean the filter!

When I first learned about combination microwave/vent hoods, I thought, these are space-saving genius.  Being a moderately tall person, I could easily lift items in and out of the microwave, the unit was not taking up any counter space, and it doubled as a stove vent hood.  However, the more I used the one in my current home, the more disappointed I was with it.  Here are the problems with most microwave/vent hood combos:

• The ventilation can exhaust directly back into the kitchen.  That’s right, those little grilles above the microwave door are the exit point of the exhaust fumes, which don’t get a lot of filtering before they come straight back into the kitchen.  The other option is to exhaust outside, which is far better.
• Microwave/vent hood combos typically do not provide the cubic feet per minute (cfm) ventilation that a standard size kitchen requires, and what little you get can be further reduced if there is more than one turn in the ductwork above the unit to the outdoors.  
• Although it’s a common situation, placing the microwave on a countertop is not a great installation either, because cooking gasses generated in the microwave are vented directly into the kitchen with no filter. 

Here’s what we recommend to get the cleanest air while you cook:

1. If you have a combination microwave/vent hood, check two things:
   1. Does the vent hood provide the correct cfm for your kitchen?  Here is an article to help you calculate whether it’s sufficient for your kitchen.  If you don’t know the cfm of your unit, type the model number into an internet search.  If your unit does not have the necessary throughput, consider placing the microwave elsewhere and getting a more powerful standalone vent hood.  In this case proceed to #2.
   2. If the cfm is sufficient, does the microwave/vent hood exhaust back into the kitchen?  Place a microwaveable container in the microwave with some water and start to heat it.  Place your hand over the grille above the door and see if you can feel a stream of air moving into the room.  
      1. If so, then the exhaust is probably set to exhaust into the kitchen.  If you own your home and you want to change it to exhaust outside, it’s possible to take the microwave down from the wall and change the exhaust configuration.  Here’s a short video on how to rotate the blower fan of the microwave, which will change the exhaust port configuration.  This change necessitates installing a duct above the microwave and vent port outside, however.  For the venting, check this video. 
      2. If you are renting or otherwise can’t change the configuration of your microwave/vent hood exhaust to outside, then do your best to clean the filter on a regular basis so that cooking particulates can be trapped before they’re blown back into the room.
2. Congratulations if you are upgrading to a standalone vent hood (our choice for the best kitchen atmosphere)!  Here are some tips to split up the microwave and vent hood and make each perform well.
   1. If budget is not a constraint, vent hoods now come in a “balanced” option, which means they not only suck fumes from your kitchen, but these are replaced with fresh air from outside.  Check out this smoke test on such a unit. 
   2. For normal budgets, good kitchen vent hoods can be purchased between $200-500 (here is a great review on the newest models, but be sure to pick one that vents externally!)  In addition to capacity, it’s also wise to get the quietest fan you can afford so that you won’t be annoyed with the sound.
   3. Now, where shall we place the microwave?  Most kitchen design professionals are happy to place it anywhere in the kitchen except the countertop, but then venting it back into the room is still polluting your indoor air.  Besides the moisture emitted from cooking steamy foods like rice or potatoes, some foods emit a lot of ultra-fine particles (UFPs).  Popcorn is one of these; in this study it was discovered that UFPs and PM2.5 generated by microwaving popcorn were 150-560 and 350-800 times higher than the emissions from microwaving water, respectively. About 90% of the total particles emitted were in the ultrafine size range.  To avoid releasing these harmful particles into your kitchen, here are the best scenarios for venting the microwave.
      1. Install it in cabinetry with a dedicated vent to the outdoors.  No questions about getting the vapors out in this case!
      2. Install it in a lower cabinet space next to the stove.  That way, steam and UFPs exhausting from the top of the unit can be drawn up and out by the range hood. “Drawer” microwaves are becoming more popular now (see photo below). 
      3. (Least effective, but still possible) Set the microwave on the counter next to the range hood but 2 feet away from it, for heat safety concerns. 

The last two options require manually turning on the range hood every time you use the microwave, but if you have a nice quiet vent hood, this shouldn’t be a problem.  

Microwave Drawer installed next to the oven/stove (source: Home Depot)

Refrigerator coils

It’s pretty obvious when the refrigerator needs cleaning: food spills inside and dirty fingerprints outside get the most attention.  However, the most important part (the working “guts” of the fridge) is easy to overlook, except for some dust gathering on the toe kick grill.  On most newer models, the cooling coils are hidden under the fridge, and all kinds of dust (especially if you have a shedding pet) will gather there and clog up the vital cooling parts. The coils should be cleaned every six months to one year to keep the fridge working properly, and keep the accumulated dust out of your air. Here’s how to clean it without a lot of hassle (realtor.com):

• If the coils are not exposed at the back of the unit, then remove the toe kick panel in the bottom front to expose them.
• Use a vacuum cleaner with HEPA filter (you don’t want to blow that dust back into the air) to vacuum off as much dust as you can reach.
• Use a coil cleaning brush to get between the rows of coils, keeping your running vacuum nearby to suck up dislodged dust. 
• Clean off the front grille with the vacuum and soap and water if necessary, and reinstall it.

The Dishwasher

Ahh, the dishwasher–what a super-convenient place to hide dirty dishes.  My cousin (an engineer) always joked that in his new house, he’s going to install 2-3 dishwashers and no cabinets.  Why?  Dishwashers are way cheaper than cabinets and no one likes to unload the dishwasher.  When you can have 1 “clean” and 1 “dirty” dishwasher at all times, you can take clean dishes from the clean one, use them and place them in the dirty one, and theoretically no cabinets are needed!  Somehow, I think his wife will have a problem with no cabinets…

Back on topic, dishwashers are appliances that use steaming hot water and caustic detergent, but are not vented to the outside.  Where does all that steam and vaporized detergent go?  Into your kitchen air, of course!  Hayward Score is a company which identifies the major issues in your home that can impact your health and gives you free personalized actionable recommendations to fix them.  They performed a study on how bad dishwashers are for your indoor air quality, and found out that it was really the “heat and dry” cycles, not the soap, that caused air quality problems.  They placed an air quality monitor in the room adjacent to the kitchen and ran the dishwasher three times:

• Dishwasher run with standard soap, heat and dry cycle on = Air Quality: RED ZONE (bad)
• Dishwasher run with no soap, heat and dry cycle on = Air Quality: RED ZONE (bad)
• Dishwasher run with standard soap, heat and dry cycle off = Air Quality: BLUE ZONE (good)

Based on these results, the soap was not causing elevated levels of VOCs but high temperature combined with chlorinated water was.

When your home is supplied by city or community water, these systems typically use a lot of chlorine to keep bacteria out.  I mean, A LOT–often you can turn on the tap and it will smell like a swimming pool coming out of your faucet.  Heat and dry cycles can reach temperatures of 160 deg F or more, which when contacting chlorinated water, produces chloroform.  The chloroform can drift through your home farther than the steam does, hence the bad air quality readings taken in the next room. 

The solution to good air quality while running your dishwasher?  If your tap water is sufficiently hot to sterilize (above 120 deg F), then don’t use the heat and dry cycle settings.  Also, run your kitchen exhaust vent during and 30 minutes after the dishwasher cycle, to move steam and any other gasses outdoors.  If your tap water is below 120 deg F, then it’s a good idea to use the heat cycles to make sure everything is sanitized, but make sure to run the kitchen exhaust vent simultaneously.

Toasters, Crock Pots, Air-Fryers, Electric Skillets and all their cousins

We have a lot of miscellaneous appliances hidden in the cabinets or sitting on the countertops, which can put a lot of fine particulates and VOCs into the air when using them.  Toasters are one of the worst offenders, and start emitting toxic fumes from the moment you turn them on (University of Texas at Austin study), because they are heating up the leftover bits from previous foods, including oils.  Toasting two slices of bread caused twice as much air pollution as is seen in London for 15 to 20 minutes – meaning three times the World Health Organization’s safety limit. (dailymail.co.uk)  The solution?  Set them as close as possible to your range (2 feet away is safe if you are using the range also) and fire up that kitchen exhaust fan.  Heck, chopping your onions next to the kitchen exhaust fan can even whisk away the chemical irritant that they release to make you cry (syn-Propanethial-S-oxide).

With a good exhaust fan and little cleaning you can spend as much time as you like in your kitchen without worrying about what’s floating around in the air! 

Can my indoor air quality affect the food I eat?

Do you ever look at the food on your countertop, whether it’s an apple pie or bowl of potatoes, and wonder, how did that food go bad so fast?  It’s a common problem, even more so in warmer climates, so we thought you’d like to know how your indoor air quality affects your food!

Admittedly, not all spoilage comes from your own air.  It’s been recognized that food processing plants need to have better air contamination control during the food production process.  “Primary  air  pollutants  in  the food  industry  are marked,  being,  in addition  to  microorganisms, suspended particles, combustion  products (nitrogen oxide,  carbon monoxide, carbon dioxide,  sulfur oxide) and volatile organic substances.” (2019 Meat Industry Conference Paper)  The contamination of food products is dependent on:

• air’s microbial load, and 

• on the duration of exposure to the air, whether during specific technological processing stages (e.g. cooling) or during storage (from book: Hygienic Design of Food Factories, chapter 14: Managing Airflow and Air Filtration to Improve hygiene in food factories).  

Air in slaughterhouses and sausage production facilities, for example, is more than 10 times more laden with yeasts and molds than dairy processing facilities, because of contamination that can come in on the product (animal feces).  The second point is that the product contact with air needs to be limited in order to limit its contamination.  Air  quality  is  particularly  important  in facilities for  production and packaging of butter, if this is manufactured in open-type mixers, since these devices can also incorporate up to 5% of the surrounding air into the product [Varnam  A  and Sutherland  J  P  1996 Milk  and  Milk  Products: Technology,  Chemistry  and Microbiology 1st ed, Chapman and Hall, London, p 451].

Another factor that causes spoilage during food processing is humidity.  There are three ways that humidity affects the food: 

• Condensation on equipment and food can accelerate microorganism growth

• Dry foods can absorb moisture that will lead to microorganism growth

• Packaging like paper and metal start to degrade, leading to spoilage

These insights into how food gets contaminated in factories are good for application in the home because although we can’t much control how it gets packaged, we can certainly control how it’s stored and prepared at home.  So let’s dive in…

The three main biological pollutants that cause food spoilage are bacteria, yeasts and molds. (online course)  Bacteria, yeasts and molds, which are typically small in size, can hitch a ride on larger particles like water droplets or dust.  Where do these come from?

The bathroom.  It’s not pleasant to think about, but “Germs will more likely spread after you flush, when bits of fecal matter blast into the air in aerosol form, a phenomenon known as "toilet plume." From there, Kelly Reynolds (a public health researcher at the University of Arizona) said, the "bits of fecal matter settle on surfaces, contaminate hands and then get spread to the eyes, nose or mouth." (USAToday.com)  Here are some ways to limit the spread of germs from the bathroom to the kitchen: 

• Close the toilet lid before you flush.

• Wash and dry hands before leaving the bathroom

• Use an ionizer like the Germ Defender in the bathroom, to kill germs in the air and on surfaces.

Pets.  Similar to the slaughterhouse scenario, many of us have furry animals (pets) walking around in our food-processing facilities (kitchens).  Where these pets have been and what they have on their fur and feet can be really disgusting!  Worse, homes with litterboxes in the kitchen, or allowing pets to walk on the counters, is like placing a toilet in the kitchen or even on the countertop!  It’s just not pleasant to think about.  If you have pets and you have a kitchen, think about these reforms:

• Bathing pets regularly so that bacteria and mold are minimized

• Not allowing pets to walk on countertops

• Keeping litterboxes in another area of the home away from the kitchen if possible

• Spraying pets’ fur regularly with a safe anti-microbial spray like Remedy Mold Treatment Spray by CitriSafe.

• Always wash your hands after touching your pets and especially before food preparation!

The refrigerator.  What?  How can the refrigerator work against us when we’re talking about food spoilage?  Actually, I’m not talking about inside the refrigerator, although that can be a problem (more on that later).  Here, let’s talk about what happens in the “guts” of the refrigerator, where the heat is actually released through the coils.  The speaker is Jeff May, a renowned air quality inspector.  

“I was sitting in my kitchen, and every once in a while, I’d start to wheeze, but just couldn’t understand why. One day, I realized every time the refrigerator turned on, I would have trouble breathing. Our refrigerator was only three years old, but in those days, the drip pan was accessible from the front. When I removed the grille and took it out, there was a pearl onion that somehow bounced into it. The onion had an inch and a half of Penicillium mold growing on it. So, every time the compressor turned on, it would blow mold spores out into the room. Every frost-free refrigerator has a heating cycle. The cooling coil gets full of ice, and you have to melt that ice in order for the refrigerator to cool. The water from that melt goes into a pan at the bottom. The heat from the compressor is supposed to evaporate the water, but very often, the water persists. There’s just not enough heat. So, if there’s any dust in that pan, mold growth ensues. And if you’re allergic to cats and dogs, and somebody had a pet in the house before you moved in, that refrigerator can be a perpetual source of allergens just from the dust that accumulated on the coils when the pets were there. We’ve had people who have just simply cleaned their refrigerator, and all of their allergies went away.” (Jeff May, during interview with author of moldfreeliving.com)

Now for the inside of the refrigerator: Ok, it seems like a no-brainer that you shouldn’t leave spilled food lying around in the fridge because it can contaminate other food by direct contact.  But using your fridge properly also prevents spoilage:

• The real reason there is a Fruits and Veggies Drawer: it controls humidity in the drawer and prevents certain foods from ripening too fast.  If there is a vent or slot on the drawer, this is used to adjust the humidity and air flow (because ripening fruits also produce a gas called ethylene, which will cause other fruits exposed to it to ripen).  Closed vent or no vent = high humidity, and Open Vent = low humidity.  For a quick way to remember what to put in the “Crisper Drawers”, remember this rule of thumb: “rot-low, wilt-high.” Fruits that are prone to rot belong in the low-humidity drawer, while produce that's prone to wilting needs to be enclosed completely in the high-humidity drawer. (for a full explanation see article at epicurious.com)

• Don’t put meat, cheese, milk and eggs in the door shelves!   The door of the refrigerator tends to stay at a higher temperature and these items will spoil more quickly (with nasty consequences) when stored there.  For more on where to store what food, this article helps a lot).

The FoodKeeper App from the FDA is a useful tool to determine how long to keep, and when to throw out specific foods.  It is also helpful to know why you need to preserve foods by refrigerating or freezing them right away (within  2 hours of cooking).  Bacteria are not killed by these colder temps, but their growth is slowed down or stopped.  Some bacteria and their endotoxins (toxins released by the bacteria through its life cycle and during death) are highly resistant to heat, so thoroughly re-heating them before eating does not kill the toxin! (check out our post on endo-and exotoxins here).  Staphylococcus aureus is one example of such a bacteria, and it can cause some serious food poisoning, even death.  

The dishwasher. Wait–the dishwasher is supposed to clean my dirty dishes, how can it be polluting my kitchen air?  If you have ever cleaned the vent on your dishwasher, you will know how absolutely filthy this spot can be.  Food residue, along with moist, steamy air will cause a thick slime to grow.  The rest of the dishwasher needs a deep clean too (not just using a bowl of vinegar and/or baking soda), but the vent especially is the area where escaping steam will carry bacteria into your kitchen air. 

Finally, keeping proper humidity in your home is super-important not only for your sinuses, but for food preservation too.  Some fruits and veggies should only be stored on the counter (check them out here), so the proper humidity will help them to stay fresh longer.  

Now you know how good air quality in your home means better food (especially in your kitchen).  By reducing the bacteria-load in the air, reducing exposure to the air, and keeping proper humidity in the air, you can waste your precious foods less, and enjoy them more!