Is one who works for an oil company in the Fire and Emergency Department, and participates in contracting with maintenance companies for the fire system—whether by signing the contract, summoning contractors, or supervising maintenance—sinful, given that they do not know the type of letter of guarantee or whether it is covered or not, or if the maintenance company paid the insurance in cash while dealing with usurious banks?

There is no harm for the administration to supervise maintenance or sign off on technical specifications. Inviting companies for contracts is permissible, and stipulating bank guarantees is also permissible. There is no need to inquire about the type of guarantee or the source of the contractors' funds. The one who signs the contract is not sinful if the company keeps the insurance amounts in usurious banks, because the sin falls upon the one who directly engages in usury or assists in it.