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!