Hi, we had the same issue. I spoke to the fit test provider and, because most of their clients are LARCs, they automatically put 12 months on all certs. There is no prescribed time period between tests, as you say it is the employer’s assessment, but HSG53 states:
86 It is also good practice to have a system to ensure repeat fit testing is carried
out on a regular basis. This is especially important when RPE is used frequently as
a primary means of exposure control, eg annual testing for workers involved in
licensed asbestos removal. If there are any changes to a person’s face through, for
example, weight loss/gain, scars etc, a repeat fit test will be necessary.
It is the above “e.g.” that drives the 12 months. Fortunately our provider said they can produce certs with 24 months, we just have to make this clear when we book the test. Thanks