In fire safety engineering, information about the expected walking speed of occupants through smoke is often one factor that is of interest to the designer. However, despite the fact that research already in the 1970s demonstrated that people tend to evacuate through smoke, little research has been performed on the topic since, and evidently, there is a lack of data on walking speed in smoke. This has created a situation where fire safety engineering assessments of the required safe escape time may be intimately associated with high uncertainties, especially for buildings in which people can be expected to evacuate long distances through smoke, for example, underground transportation systems. In order to address the lack of data on movement through smoke, 133 data points on individual walking speed in smoke are presented in this paper. The data lie within an extinction coefficient range of 1.2–7.5 m−1. In line with previous studies, it is demonstrated that the level of smoke density has a negative impact on the walking speed, whereas no significant effects of inclination, type of floor material, gender, age and height could be found in the data. In this paper, recommendations are also provided on how designers should treat the data in their fire safety risk assessments, depending on the type of risk analysis method, that is, if the designer is performing a deterministic analysis or a quantitative risk analysis. It is argued that this information can be used to reduce the uncertainty in future risk analyses involving egress calculations. Copyright © 2013 John Wiley & Sons, Ltd.