MutichannelGasSensor plus Arduino Mega

Dear Mr.

I have used a MutichannelGasSensor unity successfully some time ago, operating with Photon particle. I am currently trying to make another MutichannelGasSensor drive work in conjunction with Arduino Mega and LCD touch screen. At this moment I have not obtained much success because the readings are totally absurd or nonexistent. Sometimes I just get all the readings like -1.00 or extravagant numbers. Is there any reason why this might be happening?

I would also like to know why in the example code there is only one variable for all gases? What happens if I use a different variable for each gas?

Thanks for your help.