Note 6. Leases

Operating Leases

The Company leases various office and research and development facilities under operating lease agreements that expire at various dates through October 2050. Under the terms of the agreements, the Company is responsible for certain insurance, property taxes and maintenance expenses. The Company recognizes rent expense on a straight-line basis over the term of the operating leases. Any difference between cash payments required and rent expense is recorded as deferred rent. Rent expense for the three months ended March 31, 2022 and 2021 was $1.4 million and $1.3 million, respectively.

Capital Leases

The Company purchased equipment with total gross book value of $4.5 million under capital lease agreements, of which $0.3 million and $0.9 million was purchased during the three months ended March 31, 2022 and during the year ended December 31, 2021, respectively. Interest rates for the capital leases have ranged from 3.95% to 15.0% per annum. Accumulated depreciation for equipment acquired under the capital leases was $1.2 million and $1.1 million as of March 31, 2022 and December 31, 2021, respectively.