Filter By Certain Characters

[jonnyupton]

Hi,

I'm wanting to filter my data between three categories:

1. cells that contain O2
2. cells that contain CO2
3. cells that contain CO

I currently have the formula:

=IF(AND(ISNUMBER(SEARCH("O2",L712)),ISERROR(SEARCH("CO2",L712))),TRUE,FALSE)

If the cell (L712) contains only O2 then I get an output of TRUE - this is what I want
If the cell (L712 contains only CO2 then I get an output of FALSE - this is what I want

However,

If the cell (L712) contains O2 and CO2 then I get an output of FALSE - this is not what I want, I want an output of TRUE

Also, the formula doesn't allow the possibility of also filtering based upon CO.

Would anyone be able to suggest a formula which will output TRUE if (O2) or (O2 and CO2) are present in the taget cell (L712)?
Likewise, would anyone be able to suggest a formula which will output TRUE if (CO) or (CO and CO2) are present in the taget cell (L712)?

Thanks in advance for your help.