Fresh or filtered air can reduce your risk of catching or spreading illnesses. Opening doors and windows at home is the simplest way of improving ventilation and helps protect you, your whānau and others.

How illnesses can spread

When an infected person breathes, speaks, coughs or sneezes, they may spread particles containing the virus.

Respiratory illnesses such as COVID-19 mostly spreads by aerosols — small virus particles that can stay in the air for minutes to hours. Good ventilation helps remove virus particles in the air.

You can reduce the risk of spreading some illnesses by improving ventilation.

Ventilation when you are sick

It is important to keep the air in your room fresh. If you can, open windows on different sides of the room to help airflow.

To stop virus particles spreading, reduce airflow from your room to other parts of your home:

  • block gaps under your door with a towel or draught stopper
  • before opening the door into shared spaces, open your window for at least 5 minutes to freshen the air — close the window before you open the door
  • in a shared bathroom or toilet, close the door after you have been in the room and switch on the extractor fan, or open a window.

How to improve ventilation at home

We encourage you to let in fresh air every day, including after someone visits your home.

If you can, partly open a window about 5cm for most of the day. Or open windows for at least 15 minutes as often as possible, whenever it is practical to do so.

Try 1 or more of these ways to remove stale air.

  • Open windows or doors on opposite sides of a room to help airflow.
  • Open doors between rooms to ventilate hallways and spaces without windows.
  • In kitchens, bathrooms, and toilets, switch on the extractor fan or open a window.
  • Open higher windows wider than lower windows. This helps reduce draughts.
  • If your windows do not open, check if your ventilation system filters (cleans) the air.

When leaving windows or doors open for periods of time, consider the safety of others — especially disabled people, children and pets.

Steamed-up windows can be a sign of low ventilation.

In cold or wet weather

Try 1 or more of these ways to refresh air without letting rooms get chilly or damp.

  • Partly open a window for most of the day, for example, a 5cm opening.
  • Fully open a window or door for 3 to 5 minutes every hour.
  • Open a window whenever you leave the room, closing the door behind you.

You do not have to leave windows or doors open all the time.

In homes with heat pumps or ventilation systems

Heat pumps, air conditioners and ceiling fans do not refresh the air. Instead, they move around air already in a room. You will need to open doors or windows to remove stale air and let in fresh air.

If you have a home ventilation system, check if it recycles air or filters air:

  • If it recycles air, you need to open windows or doors to move stale air out and let in fresh air.
  • If it filters or cleans air, this helps remove stale air and reduce the risk of virus particles spreading.

In rental properties

Landlords must provide good ventilation. If you live in or own a rental property, check ventilation rules on the Tenancy Services website.

Ventilation standard — Tenancy Services (external link)

Ventilation on public transport

Virus particles can build up quickly in crowded places such as buses or trains. It helps to sit or stand close to the door as airflow will be better.

Open a window on the bus if you can. Taxis and ride-share services often ask passengers to open windows.

We encourage you to wear a face mask in closed, crowded, and confined places such as public transport.

Face masks

  • A high-efficiency particulate air (HEPA) filter can remove dust, pollen, mould, bacteria and aerosols. They can filter 99.97% of particles. You can find HEPA filters in portable and fixed air cleaning units for indoor spaces.

    They are used in public indoor spaces such as:

    • medical facilities
    • gyms
    • restaurants
    • schools
    • petrol stations
    • supermarkets
    • private indoor spaces such as homes.

    There are several issues to consider when you are using portable HEPA filters such as:

    • the size and number of air filters will depend on the size and layout of the room
    • how many people will be in the room
    • the airflow through the room, in particular, any areas without airflow
    • the acceptable noise for that location (such as a bedroom).
  • Ultraviolet-C light (UVC) can kill the COVID virus by damaging the outer protein shell of the virus. This is why being outside decreases the risk of infection.

    The amount of UVC needed to kill the virus can also damage our skin or eyes. You should shield UVC lights to prevent direct contact with skin or eyes.

    Some systems use both HEPA filters and UV light. Systems from reputable manufacturers are safe and effective. There are many other technologies on the market, some of which are safe and others potentially hazardous. If you are considering one of these, we recommend you seek advice or research the safety and efficacy.

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