Editing Urinal deodorizer block (section)

==Chemistry==
[[File:Para block.jpg|thumb|Para block]]
The chemicals composing the block vary. The original formulations were based upon [[naphthalene]] and then later [[para-dichlorobenzene]], both now known to be hazardous to health by inhalation.  In some areas, the use of para-dichlorobenzene-based blocks has been banned; in other areas para-dichlorobenzene blocks or "para blocks" are still used. {{Clarify|date=April 2024}} Para-dichlorobenzene- and naphthalene-based blocks do not readily dissolve in water/urine, but easily [[Sublimation (chemistry)|sublime]] into the air, creating a sickly-sweet odor that has anti-microbial effects.<ref name="Ross">{{Cite book | last1 = Rossberg | first1 = M. | last2 = Lendle | first2 = W. | last3 = Pfleiderer | first3 = G. | last4 = Tögel | first4 = A. | last5 = Dreher | first5 = E. L. | last6 = Langer | first6 = E. | last7 = Rassaerts | first7 = H. | last8 = Kleinschmidt | first8 = P. | last9 = Strack | first9 = H. | last10 = Cook | first10 = R. | last11 = Beck | first11 = U. | last12 = Lipper | first12 = K.-A. | last13 = Torkelson | first13 = T.R.| last14 = Löser | first14 = E. | last15 = Beutel | first15 = K.K. | last16 = Mann | first16 = T. | doi = 10.1002/14356007.a06_233.pub2 | chapter = Chlorinated Hydrocarbons | title = Ullmann's Encyclopedia of Industrial Chemistry | year = 2006 | isbn = 3527306730 }}</ref>

Many urinal blocks are now para-dichlorobenzene and [[naphthalene]] free; these water-soluble alternative blocks are made from a mixture of fragrances and [[surfactant]]s (normally [[quaternary ammonium compound]]s),<ref name=inf/>
which offer some active cleaning and antibacterial efficacy. The new water-soluble blocks improve the cleaning of the pipes which helps to reduce odor. Some recent formulations also include bacterial spores which, coupled with the surfactant cleaning power, can more completely get rid of odors and blockages caused by the buildup of solids in the [[Trap (plumbing)|traps]] and pipes. Some manufacturers claim that these "biological blocks" can enable completely no-flush [[Urinal#Waterless urinals|waterless urinals]] to be fitted.

Some urinal blocks also have enzymes added to help digest buildup within pipes.{{CN|date=November 2020}}

Autoflush<ref name=inf/> and/or [[ice]] are sometimes used as alternatives.<ref>{{cite web|last=Upton|first=Chad|title=Why Bars Put Ice in the Urinals|url=http://brokensecrets.com/2013/07/31/why-bars-put-ice-in-the-urinals/|work=Broken Secrets|date=31 July 2013 |access-date=31 July 2013}}</ref>