Background: Inadvertent injection of foreign material during angiography, particularly neuroangiography, should be avoided to reduce the risk of embolic complications. Woven gauze and cotton fabrics have been identified as sources of inadvertent foreign body embolization. Purpose: To find the source of particles that contaminate injections on an angiography table and to identify measures for their reduction. Materials and Methods: The number and size of particles on an angiographic supply table at a tertiary stroke center were analyzed by using the Coulter principle in September 2019. Seven conditions (saline directly drawn from its bag, from a small metal cup, from a small plastic cup, from a large plastic bowl, from a large plastic bowl with a guidewire and its sheath, from a large plastic bowl with a stack of woven gauze, and from a large plastic bowl with a large cotton towel) were tested at different time intervals (0, 30, and 60 minutes). Each container was filled with saline, and particle count was analyzed immediately after unpackaging, after rinsing with saline, and after introduction of foreign material; t tests were used for statistical comparisons. Results: Freshly unpacked basins can be contaminated with many submillimetric particles (range, 4.4-25.1 particles per milliliter on average, depending on basin). Cotton towels and woven gauze placed in rinsed basins resulted in a significant increase in particles (from 1.5 particles per milliliter +/- 0.4 [standard deviation] to 64.4 particles per milliliter +/- 4.1 and 257.1 particles per milliliter +/- 11.6, respectively; P < .001). Rinsing basins with saline significantly reduced the number of particles (P < /= .03). Drawing saline directly from bags through intravenous lines yielded the lowest number of particles (0.1 particles per milliliter). Conclusion: To decrease the risk for foreign body embolization, it is best to rinse all basins before use, draw saline and contrast agents directly from the respective bags and bottles through intravenous lines, and avoid cotton towels and woven gauze in basins and on the angiography table altogether whenever possible.