| Value | Category | 
                                    
                    
                        | 1 | Electricity | 
                                    
                    
                        | 2 | Gas | 
                                    
                    
                        | 3 | Petroleum/paraffin/querosene | 
                                    
                    
                        | 4 | Charcoal | 
                                    
                    
                        | 5 | Mineral coal | 
                                    
                    
                        | 6 | Wood | 
                                    
                    
                        | 7 | Animal faeces | 
                                    
                    
                        | 96 | Other | 
                                    
                    
                        | Sysmiss |  | 
                            
            Warning: these figures indicate the number of cases found in the data file. They cannot be interpreted as summary statistics of the population of interest.