37 Installation, repairs and maintenance services, especially of apparatuses and instruments for conducting, switching, transforming, accumulating, regulating or controlling electricity, apparatuses for controlling air conditioning installations, heating installations, toilets in vehicles and ships, installations for airing, aeration apparatuses, electrically powered blowers for ventilation, electric air conditioners, air conditioners for vehicles, air conditioners for ships, air conditioning filters, fans being parts for air conditioner installations, air conditioning fans, electric cool boxes, heat pumps, electric water heaters, air purifiers, demisters, defrosters for vehicles, pervaporisers