In a wireless sensor-actuator network (WSAN), sensor and actuator nodes exchange messages in a wireless channel. Sensor nodes can deliver messages to only close nodes while actuator can deliver to distant nodes. Messages sent by nodes might be lost due to collision and noise. The more number of sensor nodes are located in an event area, the more number of messages are lost due to collision. In the redundant data transmission (RT) protocol, a sensor node sends a message with not only its sensed value but also sensed values received from other sensor nodes. Even if a message with a sensed value v from a sensor node is lost, an actuator node can take the value v from other messages. We evaluate the RT protocol compared with the CSMA protocol in terms of how much sensing data a node can receive in presence of messages loss.