Grilling with charcoal is not for indoors

If you are grilling indoors with charcoal then it's very dangerous because significant amounts of toxic gases, especially carbon monoxide (CO) are released from the glowing charcoal. Even if windows, doors or the garage door are opened for "safety reasons", sufficiently high concentrations of CO leading to death may occur. This risk also exists for items that are indicated as special "indoor grills" even though they use glowing charcoal as a heat source, or in charcoal-fired cooking pots, so-called "hot pots" if they are used in the living room or in restaurants. The Federal Institute for Risk Assessment (BfR) in cooperation with BAM Federal Institute for Materials Research and Testing in a research project recently tested the level of CO concentrations that can arise from the use of charcoal grills or open fires indoors and when people become at risk. The results found that dangerous carbon monoxide concentrations are reached even after a relatively short time.

BfR has highlighted the dangers of grilling in a closed room for years, however, no data on the origin and spread over time and the spatial distribution of carbon monoxide (CO) indoors when using charcoal grills or charcoal-fired heat sources have so far been available. In order to obtain data on CO concentration during indoor grilling, BAM has performed a number of tests on 800 grams glowing charcoal. Lethal gas concentrations were quickly reached in the preliminary tests in a small measuring chamber. Since the situation in larger spaces could not be demonstrated in the small volume of the measuring chamber, additional measurements were carried out in a larger cloud chamber. Due to its 19 cubic metres volume, the cloud chamber is a good model for a small garage or living room. The CO concentration was measured both at ceiling height and directly above the grill and no significant differences were observed: the combustion gas was distributed relatively evenly throughout the room. Surprisingly, CO concentrations exceeding 3000 ppm (parts per million) occur after only two hours if 800 grams of charcoal are burnt openly. If people breathe air with such high levels, they become unconscious in a few minutes.

The data obtained by the tests serve as a basis for computer simulations and thus for a new risk assessment for grilling indoors. The simulations enable the spread of CO in any large space to be calculated. In an example, gas concentration was calculated for 42 points in the space of a conventional garage. The results of the calculations show that CO concentrations of 750 - 1100 ppm can be expected when 800 grams of charcoal is burnt in a closed garage. Clinical data indicate that 200 ppm CO in the ambient air may cause a light headache in about two hours. At 800 ppm dizziness and nausea occur. This concentration in ambient air leads to unconsciousness in about two hours.

The tests show how quickly a concentration of the colourless and odourless gas, which can lead to death, is formed. It is particularly tricky: The time window between the first noticeable symptoms and the loss of consciousness is very short. People initially often do not complain because of CO intoxication, they even look very healthy due to the cherry-red coloration of the blood pigment haemoglobin. When they try to move however, the bodily functions abruptly fail and any action becomes impossible. Furthermore, it can often be seen that even very low concentrations pose a danger because the gas is persistent and remains in the room for a long time, so accumulating in the blood if one stays in a room containing such concentrations of CO. BAM and BfR therefore strongly advise against the use of open burning material such as charcoal as a heat source indoors for grilling, cooking or heating.

The tests have also shown that smoke detectors do not protect against poisoning. The smoke detectors normally installed failed to trigger an alarm in any of the tests. Smoke detectors detect fine particles in the air that emerge from fires in large quantities. However, the gases released from glowing charcoal are almost totally invisible and cannot be recognised by an optical smoke detector. CO detectors provide an effective protection since they detect the gas itself. In the experiments in the cloud chamber, a CO detector was installed that triggered an alarm a few seconds after entering the room with the glowing charcoal in the grill, while still having the door open. With the participation of the BfR Committee "Review of poisoning", BAM and BfR will re-assess the potential hazard of the use of open, charcoal-based grills and heat sources indoors.

Source: Federal Institute for Materials Research and Testing (BAM)