The lowest pressures currently achievable in laboratory are about 1 × 10 torrs (13 pPa). However, pressures as low as 5 × 10 torrs (6.7 fPa) have been indirectly measured in a 4 K (−269.15 °C; −452.47 °F) cryogenic vacuum system. This corresponds to ≈100 particles/cm.