determined by GC/MS versus internal and external standards。For more analytical details and detection limits see SupportingInformation。

2。3。 Measurement strategy

The analysis program was carried out over three days for each fireplace oven。 On the first day, the 24 h test samples were begun for PM2。5 (indoor and outdoor) and all the continually-operating devices (temperature, humidity, TVOCPAS, CO, CO2, NOx, FMPS and OPC)。 In order to determine the background concentrations of formaldehyde and VOCs, samples were taken using a DNPH cartridge and a stainless-steel sampling tube filled with Carbotrap。The ovens were not in operation。 On the second day, new PM2。5 test samples (indoor and out door) were begun。 Then, the owners of the ovens ran them for a period of 4 h and VOC and DNPH measurements were made at 40-min intervals。 BaP was sampled indoors and outdoors for 4 h before and during the combustion phase,respectively。 The way the oven was used (lighting, putting in more wood, etc。) was accordingly documented。 Once the combustion phase was over, the continuous recording devices were stopped。

Temperature and humidity measurements took place through to the end of the PM2。5 test sample on the third day。 The owners of the ovens were asked not to use any candles or to smoke during the sampling。 Even vacuuming in the immediate vicinity of the measurement points was not allowed。 The measurements were otherwise made under normal usage conditions and ventilation behavior。 The sampling points indoors were around 2–3 m from the oven at a height of 1。5 m。

3。 Results and discussion

Wood-burning fireplace ovens are generally designed such that the fire chamber is sealed off from the room air。 The combustion products which regulation-compliant ovens generate should be completely led outside via a flue so that no emissions escape into the room。 German laws on emissions set limits on gaseous and particulate combustion products which are led away into the outside air。 Potential emissions into the indoor air are not considered。Situations can, however, also occur during proper use of woodburning ovens which lead to the indoor air being affected: the door to the combustion chamber is regularly opened to put more wood in, which of course breaks the airtight seal between the fire chamber and the indoor air at least for a short time。 Weather situations can also result in problematic pressurization effects in the flue which could also cause emissions into the room where the oven is installed。 For oven 1 an atmospheric inversion reduced the air draught from the combustion chamber into the chimney, which caused an increased release of CO and NOx into the room during the ignition phase (see Figs。 2 and 3)。 Another possibility is that leaks in an oven’s construction (e。g。 in the fire chamber door, ash box, etc。) could lead to emissions into the indoor air。The main results of the investigations during fireplace oven operation are shown in Tables 2–4 for each parameter。 The data are provided in different units (volume- and mass-related) because they are directly compared with German uideline and guidance values。 RWII is an effect-related value based on current toxicological and epidemiological knowledge of a substance’s effect threshold which takes uncertainty factors into account。 RWI is the concentration of a substance in indoor air for which, when considered inpidually, there is no evidence at present that even lifelong exposure is expected to have any adverse health impacts (Heinzow  and Sagunski, 2009; Salthammer, 2011)。 For conversion of lgm_3 into ppb and vice versa we have applied the formula 1 ppb = 0。0409 _MWlgm_3 (25 _C, 1013 mbar), where MW is the molecular weight of the target compound (Finlayson-Pitts and Pitts, 2000)。 Time dependent data are exemplarily shown in Figs。 1–5 for oven 1。 The curve progressions are fairly representative for all seven experiments。The room volume and the air exchange also play a role for each air concentration。 The houses where the fireplace ovens were tested were fitted with modern (sealed) doors and windows mean-investigations。 Generally speaking, the room temperature rose by 2–3 _C within 4 h of firing up the oven, while the relative humidity dropped as expected。 Fig。 1 shows an example of the temperature and humidity development in a 150 m3 living room with oven 1 in operation。采用燃烧热源，例如木材燃烧的壁炉，在过去几年里已经得到普及，由于不断增加的能源成本。虽然从木材炉室外排放严格监管，但是在德国，在室内释放燃烧产物很少考虑。七燃木壁炉。从2012年11月到2013年3月，对私人住宅室内空气质量进行了测试。测试中，测试前，测试后被监测。测定下列参数：超细颗粒（5。6-560纳米），微粒（0。3-20流明），PM2。5，氮氧化物，一氧化碳，二氧化碳，甲醛，乙醛，挥发性有机化合物（VOC）和苯并[a]芘（BAP）。很显然，颗粒状的物体来源于大多数烤箱。在一些情况下，也观察到室内空气中的苯的BaP浓度的增加。