Some quarantine hotels housing people who have travelled to the UK from Covid-19 hotspots are using ventilation systems that risk causing localised outbreaks, according to a report. The ventilation expert’s survey, seen by the Guardian, found that multiple hotels near Heathrow airport have systems that provide inadequate airflow or could even spread the virus, prompting calls from Labour and the Unite trade union for urgent government action. The government’s tender document, issued to firms that were bidding for contracts to provide hotel space for quarantining travellers, said rooms should have “individual ventilation systems” or windows that open safely. According to the report, almost none of the hotels near Heathrow – including some understood to be among the 16 housing quarantined travellers – allow guests to open the window to let in fresh air. This is typical in airport accommodation owing to noise and fumes. At least one of the quarantine hotels uses a heat exchange system that extracts air from inside and uses its warmth to raise the temperature of air being sucked in from outside. While this is energy efficient, the report said such systems increase the chances of spreading an airborne virus due to the mixing of airflow. “This would be the most dangerous for the cross-contamination of Covid in the air,” the report said. The report was commissioned by a hotel group that has single-room ventilation systems but missed out on the government contract. The company and the engineer who performed the survey have declined to be named. The Guardian has verified the engineer’s credentials, while experts have backed the concerns raised in the report. Ventilation systems have been cited as a potential cause of outbreaks at quarantine hotels in Australia. Alyson Prince, an infection control specialist at a London hospital, said UK hotels using heat exchange systems without open windows could face the same issue. “If they’re quarantining people who potentially have Covid and hoping to use that kind of system, there’s a problem,” she said. “There is some mix of air so there is crossover.” She also pointed to a passage in the government’s tender document that reads: “Alternatively, the hotel will have a non-recirculating ventilation system that permits redirection of the air flow from corridors and staff areas into individual’s rooms.” She said this must be a mistake as it would not make sense to direct air flow from corridors and staff areas into rooms. Dr Trupti Patel, a consultant in infectious diseases and microbiology at the University College London hospitals NHS foundation trust, said Covid-19 particles could spread in buildings without single-room air conditioning systems. “To this end it is advised that any hotel housing individuals with Covid or suspected Covid should either have no central air conditioning or have heat recovery units with windows that can be opened to allow for natural ventilation, the optimal method to boost air exchange rates,” she said. A government spokesperson said: “Air conditioning systems must not recirculate air and for those without air conditioning, they must provide adequate natural ventilation.” Unite said it would immediately take up the issue with the Health and Safety Executive (HSE) and said hotel staff could strike if working conditions were deemed to be unsafe. The union’s national officer for hospitality, Dave Turnbull, said the use of hotels without high-quality ventilation would be “another huge failure for a quarantine policy that has been littered with them”. The shadow home secretary, Nick Thomas-Symonds, said ministers must urgently reconsider the safety measures. “It’s worrying that there could be gaps in the hotel quarantine system that put staff and people staying in the hotels at risk,” he said. “This is a complex issue, but ministers have had a year to plan for this and can draw on examples of best practice from across the world. Urgent action must be taken to address these issues.” A 10-day hotel quarantine, at a cost of £1,750 borne by passengers, is mandatory for people arriving from a “red list” country. Four people who did not make themselves known on arrival at Birmingham airport were fined £10,000 on Tuesday. Travellers in quarantine hotels in England face an additional bill of up to £1,200 if they test positive for coronavirus during their stay. The Guardian put the concerns to all the relevant hotel groups. Accor, the owner of Novotel, which is housing quarantine travellers, said it did not use the kind of systems cited as a concern by experts. Holiday Inn’s owner IHG is understood to have ventilation systems that comply with government standards.