Comprehensive MultiGas Filtration: #1 Rated room air purifier for multiple chemical sensitivity (MCS) & tobacco smoke. The GC MultiGas by IQAir is a large room air purifier with the chemical removal power of over 100 gas masks. Each system uses our exclusive HyperHEPA air filter, activated carbon, gas cartridges, and post-filter sleeves to remove 99% of all contaminants.