An antiviral composition and a method of treating viral conditions comprising colloidal silver, silver nitrate, or both, and an antiviral natural herb or a natural herb from the Rutaceae family, such as Ruta graveolens, Myrtaceae family, such as Melaleuca alternifolia, Cupressaceae family, such as Thuja occidentalis, and the Moraceae family, such as unripe fig, or any combination thereof. The instrument also includes an actuator attached to the housing and a disposable loading unit configured for selective attachment to the shaft. The light condensing module includes a curving incident surface, a curving outgoing surface and a reflection surface. In this way, the pressure within the expander or evaporator can be reliably prevented from exceeding the allowable maximum pressure level. The selection of the weak alternative may include identifying which alternatives lose pairwise to the other alternatives, are excluded from the first preferences, are included in the last preferences, or have a lowest average preference ranking.