we have three different levels of limits. Depends whether swabs are taken within area of food contact surface (e.g. pipes, pumps, hands...), being close to food contact (cleaning tools...) and more far away (keyboard, wall, handle of forklift...).
tested area is 25x25 as also one customer is insisting on this. But according to the risk and the historical data we have also different frequencies for testing the areas.There are a lot of different types of swabs (cotton tip, sponge... dry, wet...) You should get the one wihich is fitting best to your situation.
Swabbing is used at our site also as cleaning verification.