Communication in confined spaces

Often times work in confined spaces requires a leap of faith depending on the risk assessment process and protocols in place .Communication is essential and in our industry (i.e. sandblasting and coating) communication is essential.Often time the environment within a confined space for blasting and painting is quite noisy and difficult for visual communication to take place...making it at times a rather risky ,if impossible task to keep in direct contact and monitor for safe operation in the space .Options such as wireless communication are unreliable given interferences that can take place within operational refineries or other types of plants where much wireless equipment is used.
One option is to use hard wired intrinsically safe units that at least are not interfered with by random wireless interrference or location of a antennaed base station.