If you have an environment where children under the age of 42 months are present or likely to have access you must install blinds which are compliant with the child safety requirements of BS EN 13120:2009+A1:2014.
The EU Decision makes it clear that this applies to all public buildings and the publicly accessible areas of commercial buildings.
Your local BBSA member can provide expert advice.
Consider “safe by design” first.
When choosing new blinds, consider one which does not contain cords or chains to operate the blind as these blinds require no additional safety devices as they are inherently safe.
Some examples are gear operated blinds where a gearbox is fitted at one end of the blind and this is then operated by a crank handle which can be permanently affixed or detachable – the latter 
is useful to prevent unauthorised use of the blind. Often gear operation is used for roller blinds in schools and other high use environments but gear operation is also available for other blind styles such as vertical blinds and venetian blinds.
Motorisation also removes operating cords and chains and allows for the blinds to be automated by linking to sensors and timers. With rapid advances in battery technology some blinds styles and sizes can be operated using rechargeable batteries meaning there is no need to have mains wiring to the blind.
External shading is inherently safe as it is fitted outside of the building and typically this form of shading is far more effective at reducing unwanted heat gain – you can see more here.
If your window size, position or shape does not lend itself to an inherently safe blind it is still possible to have operating cords and chains but they must be supplied and fitted with a compliant safety device.
In-built safety devices
These devices are built into the blind and typically involve a breakaway system where the cord or chain will part under undue pressure. The requirements of the standard are that the breakaway pressure is less than 6kg so these systems may not be ideal for high use areas.
Supplementary safety devices
Safety devices such as tensioning devices for looped cords and chains and cleats for cords can also be used and must be fitted in accordance with the instructions.
Cord and chain lengths
The child safety requirements determine the cord and chain lengths depending on the safety device used as can be seen in the chart below:
