Better gas range venting under microwave

Question

My microwave venting is not working Over my gas range. I have no access to vent outside. Is there any type of heavy duty filtering vent available to mount under the microwave or to the wall under the microwave? That will not trigger my fire alarm?

Answer 1

Is there any ... filtering vent available to mount under the microwave or to the wall under the microwave?

If the filter does not fit into the microwave itself as part of the standard equipment of the microwave, then this is not a wise idea or possibly dangerous to add a filtering device under the microwave. The add-on filter would be within the space expected to be free above the cooktop, may restrict movement of pots and utensils, and may be too close to the burners for fire risk.

Since:

• Smoke may be a concern: "That will not trigger my fire alarm?"
• Venting outside is not possible: "I have no access to vent outside."

If your microwave has built-in ducting capability which could have been used to vent outside if your home had the facilities, you can add an inline duct filter (web-search) to the output of the ducting setup on the microwave:

(not affiliated or endorsing, only examples)

Attach such a setup to the output of the microwave duct, and vent it inside the cabinet above the microwave or an adjacent cabinet. A screen panel on the cabinet door may be required to let the filtered air out, and an inline booster fan to overcome the back pressure on the microwave fan may be required.

Answer 2

Unfortunately a range exhaust that vents internally is never going to work "great" however they make charcoal filters specifically for internally vented range exhausts. Typically the filter would just be a steel mesh that catches some oil but not very much smoke. The charcoal filters do make a noticeable improvement in performance but need to be replaced more often as they are not washable.

An example of a charcoal filter:

Versus what you normally find in a range hood:

Answer 3

You Need to Vent Outside

A cooktop exhaust fan takes care of several things:

• Smoke
• Cooking odors
• Steam
• Carbon Dioxide
• Carbon Monoxide

The first three can be handled by a good filtering system.

The last two can NOT be handled by any filtering system, at least not anything available to an ordinary consumer.

Carbon Dioxide

Carbon dioxide is a normal byproduct of natural gas combustion. It is not harmful in small quantities - after all, there is always some in the air and humans produce it all the time. However, it is dangerous in large quantities. If you don't believe me, see the problems on Apollo 13. A good exhaust fan will help remove combustion air that includes carbon dioxide and fresh air, with less carbon dioxide, will come in to replace it. A fan that does not exhaust to the outside will simply recycle the same air, constantly increasing in carbon dioxide concentration.

Carbon Monoxide

Carbon monoxide is an odorless, deadly gas. It is far more deadly than carbon dioxide. It is not produced in significant quantities in normal use of a gas cooktop. However, it is produced if there is incomplete combustion, and that can happen if a burner is not functioning properly - e.g., due to spills. Carbon monoxide in small quantities can cause various symptoms that can easily be confused with the flu or other illnesses, in larger quantities it kills. A carbon monoxide detector is very helpful, and advisable in any home with combustion appliances of any type, but venting combustion air to the outside can prevent most serious problems from occurring.

Many "fire alarms" are really smoke and/or heat detectors. Some include carbon monoxide detectors as well, so if you are getting "nuisance alarms" it is worth investigating to see what they are detecting - if they are detecting carbon monoxide then you have a serious problem.

Never say "can't vent outside". OK, that may be the case if you are in a submarine or in an underground cavern or similar, and I don't recommend combustion appliances in those places. But for the vast majority of houses, the issue is not "can't" it is "expensive to do so". But usually quite possible with a bit of work. where there's a will, there's a way.