Who's aware of evap lines on a pregnancy test?

Eloise
So I've done 2 Sainsburys pregnancy tests both which come up with a very faint line (within the designated time) but both slightly off centre. I've never heard of evap lines until today, are others aware of these on a sainsburys tests? The positive line is blue, not grey. Someone help, my hopes of it being a BFP are very quickly fading?