The winter in Delhi was once a glorious time meant for holidays and weekends spent picnicking in its public parks. This is now a time of health emergency as air is so dirty you can taste and smell it. The levels of tiny particulate matter (known as PM 2.5) that enter deep into the lungs reached a toxic level in some areas, data from the System of Air Quality Weather Forecasting and Research website shows.

The Indian Medical Association has declared "a state of medical emergency" and urged the government to "make every possible effort to curb this menace". Doctors have asked people to stay indoors during the worst days. With air pollution crossing 'severe' level, here are a few tips and advisories from the WHO that can help you to take care of yourself and your loved ones during the deadly Delhi smog.

Remain indoors as much as possible: During high-pollution episodes all people, particularly those at risk, children and elderly people, should stay indoors as much as possible and away from roads with heavy traffic. External doors and windows should remain closed to reduce the penetration of pollution from outside.  

Prevent additional sources of air pollution indoors: by avoiding using anything that burns, such as wood burning stoves, candles and incense. Do not smoke tobacco products indoors.  

Pay particular attention to keeping the rooms inside homes clean: Wet mopping and dusting is preferable to sweeping or vacuuming as these can stir up additional dusts and particles.  

Limit and if possible unnecessary travel by cars, scooters and other motorized vehicles: This will not only prevent additional personal exposure but it will prevent adding to already high pollution levels for others.

Create a clean room for sleeping particularly for young children or elderly persons: A good choice would be one with few windows and doors. If the room has windows, keep them closed. Run an air conditioner or air purifier. if you are certain your air conditioner does not draw air from outdoors and has an appropriate filter.

To effectively remove airborne particulate matter a High Efficiency Particulate Arrestance or HEPA filter with a rating of at least H13 or above is needed. Avoid the use of ionization filter technology as it will generate ozone, and create additional health hazards.

To get the maximum advantage from an air purifier, you may need to carefully select where it is places inside the house. A bedroom where children or elderly are sleeping for example may offer most benefit.

Masks should be disposable, regularly changed and have a rating of at least N-95 meaning that the mask is adequate for filtering out 95% or most of the PM2.5 particles,

The fitting of the mask is very important: Masks should provide a tight seal around the wearer’s mouth and nose. This may be particularly difficult to achieve especially for children.

Finally and always important: Visit your family doctor or health clinic if you feel unwell experiencing any adverse effects from air pollution.