air-Q Lab: How useful is a tea light oven? We have measured!

Practical test with a tea light oven: The results of the air analysis with the air-Q

Before our practical test with the tea light stove could start, we ventilated our test room for ten minutes from 8:40 to 8:50. The carbon dioxide level of around 700 ppm, which had been slightly elevated until then, dropped to 450 ppm (ppm means parts per million). Then the test began and we lit the tea lights of our miniature heater at around 8:52 am.

The test phase lasted 2.5 hours from 8:56 a.m. to 11:31 a.m.: from the lighting of the tea lights to their self-extinction. During the entire time, our air-Q air meter recorded the development of air quality in the room and monitored 14 air components with dedicated sensors. During this time, some of the air sensors moved a bit - we'll go into some of the values here.

After just a quarter of an hour of operation of the tea light stove, the nitrogen dioxide (NO₂) level rose sharply. While the initial values after ventilation were not even 10 µg/m³, they reached a peak of over 75 µg/m³ shortly before the end of the test. The average NO₂ value was 48.68 µg/m³. Thus, the EU outdoor air limit values for long-term pollution are exceeded and the short-term maximum values for indoor areas are almost reached.

Surprisingly, contrary to our assumption, the particulate matter levels (PM₁ PM₂,₅ and PM₁₀) remained at a constant low level of 6 µg/m³ on average, which already existed after ventilation and was maintained by the tea light stove through minimal particulate matter emission. The reason for this is probably that the burning of the tea lights is a pure combustion process. Soot is only produced at the wick.

In addition to the other measured values, we also monitored the development of the measured value for volatile organic compounds (VOCs). The value exceeded the limit of 2,000 ppm shortly after the start of the test at around 9:10 am. The VOC load in the room then increased steadily and reached four times the limit value by the end of the test. The average level was 5,661 - well above the line marked as hygienically unacceptable by the Federal Environment Agency.

How much does a tea light stove heat?

We were pleasantly surprised! The air temperature (T) increased noticeably from 19.7°C (directly after ventilation) to 21.5°C during the time the tealight stove was running. The rise in temperature is also noticeable quite quickly due to the heat radiated by the clay pots. The flickering tea lights also create a cozy fireplace atmosphere, so that the perceived room temperature is very pleasant.

Of course, the increase in air temperature cannot be fully explained by the tea light oven, as furniture also gives off residual heat from before ventilation, but the influence was noticeable and measurable.

air-Q energy-saving tip: Turn down your heating by 1 to 2 degrees Celsius and instead let a tea light stove generate the heat to compensate.

Even two hours after our experiment, the pot of the tea light stove is still warm and the threaded rod is even hot. Accordingly, the clay pot effectively stores the absorbed heat and releases it over a long period of time. Even if the heat is no longer enough to heat your room, it is definitely enough to warm your hands or feet.

How dangerous is it to heat with a tea light stove?

To supervise the burning tea lights, one person was always present in the room during the test. This naturally also caused the increased CO₂(carbon dioxide) values, which were due not only to the burning candles but also to the breathing of the test leader. As an initial CO₂ value, the air-Q detected just under 450 ppm. After the start of the test phase, the value rose sharply within just under 45 minutes, reaching its first peak of over 1,000 ppm three quarters of ten. Another hour later, the second peak was exceeded at over 1,200 ppm. The average carbon dioxide level was 912 ppm.

Our measurement data also show a clear exceeding of the carbon monoxide limits when operating the tea light stove. This can quickly become dangerous. Carbon monoxide (CO) is a colorless, odorless and tasteless, but very toxic gas. Carbon monoxide interferes with oxygen saturation in the blood because it can attach itself approximately 210 times more strongly to the hemoglobin present in the blood. Even at a saturation of 1.28% carbon monoxide in the room air, you risk suffocation within one to two minutes.

If you want to heat your room with such a stove, it is therefore highly advisable to check the development of the room air for increased CO values. If your air measuring device indicates a high carbon monoxide level, you should definitely ventilate the room.

Other precautions you should take when heating with a tea light stove:

• Place your tea light stove on a fireproof base.
• Do not leave the tea light stove unattended. Since the tea lights are close together, the heat here can multiply and cause a wax fire.
• If a wax fire should occur: Smother the flame with a fire blanket. Attempting to extinguish the fire with water could provoke a pilot flame.

Using the air-Q air analyzer, we were able to track 14 relevant air components that were influenced by the operation of the tea light oven. Thanks to the air analyzer, the tea light oven can be operated safely in future, as all air components and limit value violations can be checked. If you pay attention to pollutants and ventilate regularly, a tea light heater can help you to heat your home in winter and save energy.

(Contributing photo: air-Q)