Susceptibility to two pyrethroids in Boophilus microplus (Acari: Ixodidae) populations of northwest Argentina

An improved flexible respiratory mask facial seal, as well a respiratory mask incorporating such seal. The facial seal comprises an annular member including a peripheral sidewall bounded by an inner end and an outer end generally opposite the inner end. The inner end is adapted for attachment to the shell or body portion of a respiratory mask and the outer end defines a contoured sealing surface adapted for confronting sealing engagement with a user's face. The annular member is formed of a gel substance possessing resilience characteristics corresponding to those of human fat tissue. Preferably, the annular member is encapsulated in a thin, pliable, membranous covering to enhance the durability and washability of the facial seal. Because the facial seal simulates the resiliency of human fat tissue, the user experiences the sensation of a natural substance against his skin when the mask is donned.