The Internal Revenue Service is recalling approximately 10,000 employees to handle “mission-critical” work on-site at agency offices on Monday — and it’s requiring them to bring their own protective masks.

According to an internal IRS email released by Democratic lawmakers on the House Ways Means Committee over the weekend, agency employees who are coming in to answer phones, open mail, and handle other tasks will need to bring their own masks, even if they’re homemade.

“Although the IRS is seeking to procure personal protective equipment (PPE) such as masks and gloves, each IRS facility may not be able to initially procure the PPE for all employees immediately,” the email, from IRS human capital officer Robin Bailey and deputy human capital officer Kevin McIver, reads.

“Employees are therefore required to bring personal face coverings for their nose and mouth area when they come to work,” the email continues. “As stated in the CDC recommendations, these face coverings can be fashioned from common household materials, such as clean t-shirts or bandanas. Materials used to create the covering must be conducive to a professional work environment and not contain any images or text that may be deemed inappropriate or offensive to others.”

After the release of the email, the service clarified that it expected to be able to provide PPE for most employees this week — and that it would initially be seeking volunteers with incentive pay. A statement from the National Treasury Employees Union noted that if enough employees do not respond, the service will begin requiring employees to return to work at physical IRS offices.