The kitchen has poor suction and smells the neighbor’s cooking fumes? Budget guide for "shared flue backfill" and smoke check valve modification in old apartments in Taipei

In old apartments, period mansions or even some new housing buildings in the greater Taipei area, many homeowners often encounter an extremely annoying home experience: even though they are not cooking today, as soon as they walk into the kitchen, they can smell the strong fumes from the neighbors next door or downstairs who are frying sesame oil chicken and fried pork ribs. What's worse is that sometimes when you turn on the range hood at home, the fumes in the kitchen seem to be unable to be discharged, and the house is still filled with smoke. Long-term inhalation of these oil fumes containing heavy metals and carcinogens not only endangers the respiratory health of your family, but also makes the kitchen walls covered with sticky yellow grease. The reason behind this is not that your range hood is broken, but that it is caused by "design defects in the shared flue" and "leakage in the exhaust duct". This article will give you an in-depth look at how to retrofit a smoke check valve and provide a reasonable budget guide for Taipei.

Physical traps of shared flues: Why does your neighbor’s oil smoke drift into your home?

In most collective housing in the Shuangbei area, the kitchen fume in the entire building is exhausted to the top floor through a "public flue (shaft)" that runs vertically through each floor. When your neighbors are cooking, their range hoods forcefully blow hot air and fumes into the common flue. At this time, the air pressure in the public flue will rise. If:
1. There are holes in the joints of your exhaust pipe: If the junction between your exhaust hose and the wall flue hole is not sealed with fireproof mud or sealing tape, the high-pressure oil fumes in the public flue will escape through the gap into the mezzanine of your kitchen ceiling, and then drift into the living room.
2. The windshield of the range hood is not airtight enough: The outlet of the traditional range hood is only equipped with a simple plastic gravity windshield. When you don't turn on the phone, this windshield only relies on gravity to close, and the air tightness is extremely poor. The oil fumes between the ducts can easily blow open the windshield and flow backwards along the air ducts into your kitchen.

The hidden reason for the poor suction of the range hood: incorrect configuration of the exhaust hose

Some homeowners think that the lack of suction in the range hood is due to the aging of the motor, but in many cases it is a problem of too much resistance in the air duct:
* If the exhaust air duct turns more than twice, or is bent at a 90-degree right angle, it will cause great wind resistance, causing the exhaust efficiency to drop by more than 50%.
* After many years of use of aluminum foil air ducts, the inside of the pipe wall will be filled with thick heavy oil. Coupled with the aging of the material, the air duct may collapse, sag, or be damaged and leak, causing oil fumes to leak directly into the ceiling without reaching the shared flue.

Anti-smoke modification strategy to completely solve the problem of oil fume backflow

To solve the problem of kitchen fume backflow, the most effective and fundamental modification methods include the following three methods:
1. Install an "anti-smoke check valve" (check valve): This is the core equipment for kitchen smoke prevention. It is installed between the exhaust vent of the range hood and the aluminum foil tube. The check valve is equipped with high air-tight double blades and rubber sealing rings. When you turn on the machine, the wind will blow open the blades to exhaust smoke; once the machine is turned off, the blades will be forced closed by strong springs or gravity to block external oil smoke. If you have sufficient budget, you can choose an "electric check valve", which opens and closes synchronously with the range hood and has the strongest sealing performance. The simple pneumatic check valve with materials is about NT$ 1,500 to NT$ 2,500; the electric check valve is aboutNT$ 3,000 to NT$ 5,000.
2. Renewal and straightening of smoke exhaust aluminum foil ducts: Remove the aging and oil-filled aluminum foil ducts and replace them with new thickened aluminum foil ducts. During construction, the air ducts should be kept in a state of "straightening, no bending, and being discharged into the flue at the shortest distance" as much as possible. The cost of complete work with materials is about NT$ 1,000 to NT$ 1,800.
3. Wall flue hole sealing project: After inserting the new air duct into the shared flue hole in the wall, anti-mold foaming agent or high-temperature aluminum foil tape must be used to "completely seal" the annular gap between the air duct and the wall hole to prevent the odor between the pipes from drifting into the ceiling interlayer. This is usually done in conjunction with the above-mentioned installation, and the plumber and electricity master may charge several hundred yuan in materials wages.

Homeowner supervision and pit prevention indicators

1. : Before purchasing a check valve or air duct, be sure to confirm the size. Common specifications in Taiwan are 5.5 inches and 6 inches. Buying the wrong specifications will result in failure to connect. If you force the tape to stick, the high-temperature oil fumes will dissolve the glue over time and cause air leakage again.
2. : After installing the check valve, the wind cutting sound during air extraction may become slightly louder due to the extra layer of blade resistance. If there is a sharp whistle when starting the machine, it means that the check valve is stuck or not fully opened, and you should ask the master to readjust it.
3. : Since the check valve is exposed to oil fume every day, after about 3-5 years of use, the blades may not be able to close flexibly due to oil dirt sticking. It is recommended that families who are accustomed to deep-frying and oily cooking can regularly ask professional kitchen appliances personnel to disassemble, inspect or replace their appliances.