Your certified sweep will evaluate your chimney externally and be looking for signs that the chimney is safe to use and compliant to part J of building regulations. 
Your chosen sweep will introduce themselves to you and ask which appliance you required sweeping and if you have had any issues from your stove, fire, or appliance.

Your certified sweep will lay down sheeting to protect your floor, and they will place their equipment on this sheet. A certified sweep will NOT place any equipment directly on your floor! They will always treat your home with respect and cleanliness. The sweep will always use blocking off methods (sheets. Sponges etc) to ensure that no soot escapes during the cleaning process.

In the process of sweeping, they will ensure that the brush has exited the flue and is seen! The certified sweep may inspect your flue with a camera, and more all certified sweeps will do a smoke evacuation test to ensure your appliance is safe to use. They will certify the work and leave you with a certificate of compliance, so you know you are safe to use your fire.

If there are any issues the chimney sweep will bring this to your attention, and in some cases where an appliance is life threatening, they will issue a warning certificate to state that the fire is unsafe and give you clear advice on what to do to rectify the issue.