In current domestic construction field, several factors influencing the safety for field workers are various due to the size and complexity of construction works involved. Among the factors, the age is the important one, because the average age of workers is getting older due to the 3D phenomena in construction fields. The safety for workers of all ages is important, but especially safety for the old, is more important. Thus, the fundamental techniques for placement of field workers with adequate safety corresponding to complexity and hard works are investigated through analyzing fatigue and heart rate of individual worker, especially for the old.