In addition to Utrecht, the heating alert also applies in North Holland, Flevoland and Friesland. “By not firing, you prevent health problems and (odour) nuisance for yourself and those around you,” according to the RIVM. The smoke is always harmful, but when the wind blows, harmful substances spread faster. People with respiratory or cardiovascular diseases, the elderly and children in particular can suffer if there is a lot of heating in their neighborhood when there is no wind. “They get more and sooner complaints when inhaling smoke,” according to the RIVM.