**6.7 Personal respiratory protection**

It is an indirect mitigation technique. In the environments where radon daughters' concentration exceeds 1.0 WL, miners should wear respirators approved by the National Institute for Occupational Safety and Health (NIOSH). The use of personal respiratory protection against radon daughters must be limited to temporary situations

**Figure 10.** *Typical freeze wall insulation [22].*


### **Table 3.**

*Mining methods and ventilation types [4].*

where engineering controls have not been developed or for maintenance and investigative work. For exposures up to 10 WL, proper filter-type respirators are available where concentrations of radon daughters exceed 10 WL, air devices, or face masks containing absorbent material capable of removing both radon and its daughters [7].

### **6.8 Dust control and miscellaneous measures**

Airborne radon progeny (daughters) has an electrical charge associated with it; so, it can be attached to dust and other particles, which can be inhaled into the lungs of mineworkers who work in the dusty environment, particularly near the working faces. Some of the best practices that can help control radon levels in the mine atmosphere include implementing appropriate dust control measures by using air filters, measuring the performance of blasting practices at the end of the shift, and minimization of main/auxiliary fan shutdowns. Abd et al. [23] showed that the radon diffusion coefficient and diffusion length reduce significantly with increased water saturation of the material. This phenomenon can be used to reduce the rate of radon diffusion into the mine air.

### **7. Summary**

Several radon mitigation techniques, particularly bulkheads and sealant coating, are being successfully used in the underground mines in the United States. Activated charcoal bed and oxidizing agents are also viable options for treating the contaminated air locally, especially at the difficult mine working faces. The feasibility of the application of these agents in the challenging mine environment needs a greater in-depth study.

Even though sealant coatings and bulkheads effectively control radon gas concentrations in the active working areas, improvements to reduce the costs and design of application of sealants and bulkheads can be performed.

Activated charcoal beds present a viable option for radon mitigation, but a pilot study in the mine environment can be more helpful to understand their applicability and effectiveness.

### *Mining Technology*

The use of strong oxidizing agents to remove radon from the contaminated mine air can also be a possibility. However, high humidity and temperature conditions in the mine atmosphere might limit the applicability of a corrosive oxidizing agent inside the mine.
