268.- Sheltering, vhich is a very expensive protective measure, inplies hardeningagainst nuclear-weapon effects rather than avoiding then. rn nucliar waro shelterswould have to protect against ionizing radiation as weJ-L as blast, cofl-a.ps.rngbuildings and flying debris, thermal radiation and fire. shelters that offerreasonable protection against rnechanical loads wou.Id, generally speaking, giveadequate radiation shielding. Special shelter design features lro;ld be necessaryoho\^rever, to deal with the extended air blast of nuclear veapons. Difficult problemsuoui-d also be the long-lasting thermal load on a shelter buried und.er a large heapof smou-ldering rubble and. the ventilation of the shelter under these conditions,Filtration of the incoming air vould be desirabfe to keep our radioactive dust andtoxic gases. Crdinary filters d.o not, however, renove the carbon monoxidegenerated. by smouldering fires. 269. Food, water and sanitation r.rould have Lo be e'vaitahle aq lcnnt,- r.iohr. h,l,c r^stay in shetter for a long time after a nuc.rear;.;;;;l;-;";;u";;:';f;."";;;;"- "" fallout radiation or because tescue work was seriously ittrpeded. Under hea.ry fall-outconditions, as wou-l-d prevail for instance about 30 lqr dor^mvind of a ]-l{t. fissionsurface-burst, people could leave their sherters after two d.ays, provided that theyA"/35 /392 English Annex could leave the contaminated area innediately and be outside it in an hour or two. If such evacuation r,rere not possible and they had to remain on the spot for a l'l1rinlFr.r rl.r'rc thFr. '.,^rr'l d h.irF r^ e1-arr ir el-ar1-are fnr. a yr^h+h if aeui.e radiation injuries r/cre to be ".voided, One hundred km dolnwind, the corresponding tines vould be a few hours arrd a r,reel-,, respectively. Tn both these instanees, there rrould be a high incidence of late radiation cancers anong the survivors, even if fha --.^ar <ha] +aFind ^oriods cou]d be observed.. 270. Rescue efforts in a nucl-ear war \,/ould pose special probl"ems because of the enontrity of the operetion involved and because of the possible existence ofresidual radia"tion. There r,rou-ld be rnany fires to extinguish and large masses of dnhrjc fram .^_1 1.^c6.t h]r.i1^.i--^ r+ ..^rr't/i h^+ laa h^<ail1tc l-^ .. -*rrq-Lncs uo reJrlovc. tL w---* -, -- assLgn such resources that al1 survivors tralped in shelters or basements could be saved, avan if <nnhi<rinalpd rlicac+cn hlanc h^rl naan Yll.onarad in adrrenne, 27I. The r:resence of fallout r.iould necessitate equipment and routines for srtrvew:np ..hF r.o,.r..Fr ir rl.cd r-ar end rnnitn*inr fhe radiation. There rrould be a.
**Analysis**
The text discusses the challenges and requirements for building and maintaining shelters in case of a nuclear war, including the need for radiation shielding, ventilation, and filtration. It also touches on the importance of food, water, and sanitation, as well as rescue efforts and the presence of fallout. These topics suggest that the text is related to disaster preparedness and response, which is often a humanitarian aid and relief effort.

**Category**
Humanitarian aid and relief