VOCs　exist　widely　in　both　indoor　&　outdoor　environment,　and　have　been　known　as　the　most　hazardous　materials　which　affect　public　health　and　welfare　owing　to　their　toxicity　potential,　carcinogenicity　and　stability.　VOCs　are　recognized　as　causative　agents　of　the　sick-building　syndrome,　in　which　formaldehyde　(HCHO)　is　one　of　them.　HCHO　has　been　classified　as　a　suspected　carcinogen.　HCHO　is　known　to　cause　nasal　tumors,　irritation　of　the　mucous　membranes　of　the　eyes　and　respiratory　tract,　and　skin　irritation.　Because　of　the　increasing　concern　on　HCHO　in　the　indoor　environment,　the　abatement　of　HCHO　is　of　significant　practical　interest　at　low　temperature,　especially　at　room　temperature.　The　conventional　technique　to　remove　VOCs　is　activated-carbon　adsorption　method,　which　needs　to　replace　and　dispose　the　adsorbent.　The　disposal　of　activated-carbon　will　cause　the　next　environmental　problem.　The　alternative　methods　are　ozone　oxidation　method,　catalytic　combustion　method,　non-thermal　plasma　method,　etc..　The　ozone　oxidation　and　the　non-thermal　plasma　methods　involve　NOx　emission　and　high　initial　cost.　The　catalytic　combustion　method　requires　a　heat　source,　hence　it　is　a　highly　energy-wasting　process　when　VOC　concentrations　are　low.　In　this　chapter,　two　kinds　of　HCHO　decomposition　technology　were　investigated,　that　is,　photo-catalytic　degradation　and　non-thermal　plasma　technology.　Photo-catalytic　degradation　of　VOCs　on　UV-illuminated　titanium　dioxide　(TiO2)　is　proposed　as　an　alternative　advanced　oxidation　process　for　the　purification　of　water　and　air.　Non-thermal　plasma　(NTP)　has　great　industrial　potential　and　has　been　applied　to　the　decomposition　of　VOCs.　At　the　same　time,　NTP　technology　has　disadvantages　such　as　low　energy　efficiency　and　undesirable　byproducts　such　as　NOx.　So　the　combination　of　NTP　with　photocatalyst　technology　was　used　in　our　investigation.　Nano-structured　TiO2,　Ag/TiO2　and　Ce/TiO2　thin　films　were　prepared　by　sol-gel　method　at　room　temperature　and　used　in　the　photo-catalyst　reactor　for　HCHO　decomposition.　The　effects　of　doped　Ag/Ce/TiO2,　relative　humidity,　oxygen　concentration,　initial　HCHO　concentration,　UV　light　wave　length,　TiO2　amount　on　HCHO　decomposition　were　investigated.　At　the　same　time,　destruction　of　formaldehyde　by　means　of　NaNO2　ferro-electric　packed　bed　dielectric　barrier　discharge　plasma　in　a　coaxial　cylindrical　reactor　was　carried　out　at　atmospheric　pressure　and　room　temperature.　The　difference　among　four　kinds　of　NaNO2　ferro-electric　reactors　was　compared　in　terms　of　specific　energy　density　(SED),　energy　yield　(EY),　and　HCHO　decomposition.　Three　kinds　of　catalysts,　that　is,　TiO2,　BaTiO3,　or　TiO2　&　BaTiO3　were　tested　for　HCHO　removal.　Effect　of　catalyst　carrier,　catalysts,　and　catalyst　amount　on　specific　energy　density　(SED),　energy　yield　(EY)　and　HCHO　removal　efficiency　were　investigated.　In　addition,　the　by-products　were　detected　and　the　mechanism　of　HCHO　degradation　was　performed.　©　2015　by　Nova　Science　Publishers,　Inc.　All　rights　reserved.