Properly designed alarm systems can benefit operators in conducting routine and emergency tasks. With the digitization of main control rooms, the alarm interface can be designed in various ways that are different from the traditional "alarm tile" style. An innovative alarm bar interface is proposed in this paper. A preliminary lab experiment was conducted to compare the traditional alarm tile and the new alarm bar interfaces. Sixteen university students were recruited to participate in the experiment, in which two emergency scenarios, Loss of Coolant Accident and Steam Generator Tube Rupture, were tested. The experiment task included two parts: alarm detection and identification. The subjective ratings supported the innovative alarm bar design for better parameter trend perception. The objective performance measures showed that the simpler design of the alarm tile interface better aided the alarm detection performance, whereas the alarm bar interface had almost the same alarm identification performance as the alarm tile interface. Relevance to industry: An alarm system is critical for a complex industrial system. The experimental results show that design evaluation is more complex than it may seem. Although it has not been proved to be overwhelmingly superior to the tile design, the alarm bar design shows promise for aiding operators and needs to be further validated. (C) 2014 Elsevier B.V. All rights reserved.