The Environmental Protection Agency (EPA) has information on products which protect you against insects and/or ticks. Check out products and compare them for hourly protection. Note that some manufacturers do not want their product protection time listed.
The LDA is an EPA Pesticide Environmental Stewardship Program (PESP) partner. PESP is a program which is trying to control pests (in this case, ticks) with the least amount of pesticide use.