Inhalation is the major route of phosphine toxicity. Odor is not an adequate indicator of phosphine's presence and may not provide reliable warning of hazardous concentrations. The OSHA PEL of 0.3 ppm is within the range of reported odor thresholds. Phosphine is heavier than air and may cause asphyxiation in enclosed, poorly ventilated, or low-lying areas.
Children exposed to the same levels of phosphine as adults may receive a larger dose because they have greater lung surface area:body weight ratios and increased minute volumes:weight ratios. In addition, they may be exposed to higher levels than adults in the same location because of their short stature and the higher levels of phosphine found nearer to the ground.