There are two types of exemption Absolute and Qualified. Those exemptions defined as Absolute do not require a Public Interest Test.
Absolute Exemptions
Where an absolute exemption applies, there is no right to the information under the Freedom of Information Act 2000.
Section 21 - Information Accessible by Other Means
Section 23 - Information Supplied by, or Related to, Bodies Dealing with Security Matters.
Section 32 - Court Records
Section 34 - Parliamentary Privilege
Section 36 - Prejudice to Effective Conduct of Public Affairs
Section 40 - Personal Information
Section 41 - Information Provided in Confidence
Section 44 - Prohibitions on Disclosure
Qualified Exemptions
Section 22 - Information intended for future publication
Section 24 - National Security
Section 26 - Defence
Section 27 - International Relations
Section 28 - Relations within the United Kingdom
Section 29 - The Economy
Section 30 - Investigations and Proceedings Conducted By Public Authorities
Section 31 - Law Enforcement
Section 33 - Audit Functions
Section 35 - Formulation of Government policy
Section 36 - Prejudice to the effective conduct of public affairs
Section 37 - Communications with Her Majesty
Section 38 - Health and Safety
Section 39 - Environmental Information
Section 42 - Legal Professional Privilege
Section 43 - Commercial Interests
Those exemptions defined as Qualified require a Public Interest Test. The main criteria to be considered is - does the public interest in withholding the information outweigh the public interest in disclosing it?
Further details of the Freedom of Information exemptions can be found on the Information Commissioners Office website http://www.ico.gov.uk/