A respirator’s Nominal Protection Factor (NPF) is the theoretical protection level based on laboratory measured performance data.
An Assigned Protection Factor (APF) is the level of respiratory protection that can realistically be achieved in the workplace by 95% of adequately trained and supervised wearers.
For example in the UK, Germany and Finland, the APF should be used when selecting a respirator.
In countries, like the U.K. yes, fit testing is required.
But keep in mind that there are no uniform European regulations in force requiring fit testing. Some companies based in countries where fit tests are required by national regulations also require fit testing to be performed in their European subsidiaries.