**5.2 Safety**

Even more important than the safety of materials is the safety of personnel, which should be a top priority when implementing a decontamination system. Safety should be considered from the perspective of normal operation as well as in the event of an accidental exposure. Under normal conditions, devices which can be operated remotely create a layer of isolation between the decontamination system and the human operator, allowing for implementation without direct contact for personnel. In the unlikely event of an accidental exposure, higher concentration solutions may come with risks for exposure to high-consequence chemicals either from contact or inhalation [39]. Choosing a product with lower operating concentrations may likewise decrease the potential for risks associated with accidental exposure caused by unintended fog leakage [38, 40]. As with most gaseous systems, the Occupational Safety and Health Administration (OSHA) has defined a minimum reoccupation level, Permissible Exposure Limit (PEL), which must be considered: ClO2 = 0.1 ppm; H2O2 = 1 ppm; and formaldehyde = 0.75 ppm. Technologies employing lower operational ppm may reach reoccupation levels more quickly due to a lower peak threshold [15, 16, 76].

#### **5.3 Consequences of repetitive use**

Decontamination within facilities is a recurring need, so both the physical devices as well as the chemicals or solutions used in them should be reviewed for the consequences of regular use. Devices with instructions requiring the operating machinery to remain outside of the room being disinfected may call into question the safety of exposed laboratory equipment within this space [34]. Likewise, systems with operating concentrations that can condense at levels beyond known material compatibility, such as 45% hydrogen peroxide, may also damage laboratory equipment [33].

#### **5.4 Ease of use**

Decision makers should critically examine the number of parts necessary for implementing a system. Multiple components may appear to create value but instead may only introduce complication and risks. Hosing laying on the floor add contamination risk in two ways: (1) hoses may impede a complete disinfection of any surfaces they touch and (2) those same hoses may contribute to cross contamination as they are moved throughout the facility. Additionally, a system with many components also comes with many opportunities to misplace or damage a critical element, potentially disrupting scheduled disinfection cycles. Quality and durability of the equipment is paramount as well.

While not strictly required, the degree of support available also contributes to the ease of use of a system. Whether creating new protocols, training personnel, or troubleshooting unique challenges, ensuring there is a commitment from the vendor to provide support can mean the difference between a quick phone call or time spent deciphering a 100-page manual.
