One of the signatories of the open letter was Marwa Zaatari, a member of ASHRAE, who compiled a list of public information on school district spending in relation to the ionization products. In response to this and her statements in the media that independent research hasn't corroborated the claims of GPS Air, the company filed a lawsuit against Zaatari in April 2021 for $180 million. Additionally, GPS Air filed a lawsuit earlier in March 2021 against Francis J. Offermann, President of the consulting firm Indoor Environmental Engineering, for the publication of an article in the firm's newsletter critical of the company. A third lawsuit was filed against the academic publishing organization Elsevier for their publication of studies, including one by Colorado State University professor Delphine Farmer, on GPS Air's devices showing their lack of efficacy.
