The present invention accurately manages the number of fine particles in a workspace and prevents fine particles from mixing with an experimental material. An isolation device for supplying a workspace with clean air resulting from dust filtration by an air cleaning means, said isolation device being provided with: a measurement probe that is for air intake and is disposed in the workspace; a particle counter for measuring the fine-particle counts for a plurality of particle sizes in the workspace air taken in by the measurement probe and outputting the measurements; a storage unit for storing, for each of the plurality of particle sizes and for work times and non-work times, management fine-particle counts at which the number of fine particles per unit volume is determined to be large; a cleanliness determination unit for determining cleanliness by comparing the fine particle counts for the plurality of particle sizes measured by the particle counter and the management fine-particle counts for the plurality of particle sizes stored by the storage unit; and an output unit for outputting an alarm if the cleanliness determination unit determines that the work-time/non-work time fine particle count for a particle size in the workspace during operation exceeds the corresponding management fine-particle count.