Many of us are now heading inside, returning to schools and offices, especially as it turns colder

Scientists and engineers say good ventilation could be a crucial way of avoiding coronavirus indoors

So what should we be looking out for?

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If you walk into a room & air feels stale there may be issues with ventilation

Confined spaces can lead to "airborne transmission" of the virus; the Chartered Institute of Building Service Engineers suggests if it seems stuffy, you should consider leaving
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A study looking at a restaurant in China blamed a certain type of air conditioning unit for spreading the virus

A split air conditioner recirculates the air, and could be more of a risk if you’re nearby for hours

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In buildings where windows are sealed check the "fresh air ratio"

Ventilation systems extract stale air from rooms and then mix with outside air and send back

Professional advice is to maximise fresh supply to reduce the risk of recirculating the virus

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Modern ventilation systems have filters which can be checked

In the US, scientists investigating a spread in a hospital found traces of coronavirus were trapped by filters, but some slipped through

Swabbing filters could reveal if anyone has coronavirus

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Look out for draughts

Experts are worried that if an infectious person sits by an open window, they could pass the virus downwind

But, it's important to remember the benefits of fresh air diluting the virus will outweigh this risk, scientists say

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Read more about how to avoid coronavirus indoors, as @davidshukmanbbc examines the science: http://bbc.in/CoronavirusIndoors