Exposure can be limited by the use of Administrative controls (eg, limiting the number of people exposed to hazardous conditions) Engineering controls (eg, enclosures, ventilation systems, safe clean-up procedures) Product substitution (eg, using safer, less toxic materials) Respiratory protection devices (eg, respirator, dust mask, gas mask) Many clinicians erroneously assume that a patient who has used a respirator or another respiratory protection device has been well protected.