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Percussion drills can be used in one of two modes. In rotary mode, they usually have vibration levels below 2.5M/s^2 and therefore do not represent a risk to the user.
Percussion drills used in hammer mode have a higher level of vibration and under heavy use conditions may need to be monitored.
When assessing exposure levels it is important to understand the split between rotary and hammer mode. A typical heavy percussion drill user may run the product for 70 hours per year, only 30-40% of likely to be in hammer mode (higher risk) with the remaining 60-70% being in rotary mode (lower risk).