Radon and Its Decay Products - American Chemical Society

Chapter 38

Modified Design in New Construction Prevents Infiltration of Soil Gas That Carries Radon 1

2

Sven-Olov Ericson and Hannes Schmied 1

Radon Consultants, Edsviksvägen 33, S-182 33 Danderyd, Sweden AIB Consulting Engineers, P.O. Box 1315, S-171 25 Solna, Sweden

Downloaded by RUTGERS UNIV on December 30, 2017 | http://pubs.acs.org Publication Date: February 5, 1987 | doi: 10.1021/bk-1987-0331.ch038

2

Dwellings located on permeable soil with strong exhalation of radon often get a contribution to indoor radon from infiltrating soil gas carrying radon from the ground into the building. 100 dwellings have been built on radon dangerous land with different modifications in design and construction in order to prevent infiltration of radon. Tight construction, ventilated crawl space, ventilation/depressurization of the capillary breaking layer (crushed stone), and mechanical ventilation with heat recovery by air to air heat exchangers or heat pumps have been tested. Added building costs and measured concentration of radon after construction and 3-5 years later are reported. It is concluded that it is possible to build radon protective and radon safe dwellings on any land. The added costs have ranged from zero to 4% of total building costs. Radon from the soil enters into buildings by convective flow of soil gas. Transport by diffusion is normally insignificant. In houses with very high radon concentration, diffusion need not be considered because it can only provide an insignificant fraction of the source strength. There are three conditions necessary for infiltration of soil gas containing radon into the building from the soil: - there must be an open connection for gas flow from the soil into the building, - there must be a driving force to produce the flow through the opening, i.e. a pressure gradient with negative pressure in the building relative to the soil, and - there must be a large enough volume of permeable soil subjacent to the building to supply the necessary radon. They are important aspects to be considered in new construction on land where protective or radon safe design is recommended. 0097-6156/87/0331-0526$06.00/0 © 1987 American Chemical Society

Hopke; Radon and Its Decay Products ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

38. ERICSON AND SCHMIED

Modified Design Prevents Infiltration

527

Recommended S t r a t e g y f o r C o s t - E f f e c t i v e Radon P r o t e c t i v e and Radon Safe C o n s t r u c t i o n Based on o u r e x p e r i e n c e w i t h r e m e d i a l a c t i o n s and m o d i f i c a t i o n s o f d e s i g n i n new c o n s t r u c t i o n we recommend t h e f o l l o w i n g s t r a t e g y f o r making new b u i l d i n g s ( s l a b on grade, v e n t i l a t e d c r a w l space o r f u r n i s h e d basement) radon p r o t e c t i v e o r radon s a f e i n a c o s t e f f e c t i v e way:


- A v o i d open c o n n e c t i o n s t o t h e s o i l . - R e i n f o r c e d c o n c r e t e o f s t a n d a r d q u a l i t y g i v e s enough r e s i s t a n c e t o p r e v e n t c o n v e c t i v e f l o w o f s o i l gas p r o v i d e d t h e r e a r e no major c r a c k s o r o t h e r o b v i o u s openings. Our r e s u l t s v e r i f y e a r l i e r Canadian c o n c l u s i o n s ( C e n t r a l Mortgage & Housing Corp., 1979) t h a t a m o n o l i t h i c s l a b w i t h c a r e f u l l y s e a l e d u t i l i t y e n t r a n c e s w i l l p r e v e n t i n f i l t r a t i o n o f radon. Connections w i t h basement w a l l s and any j o i n t s must be c a r e f u l l y s e a l e d and s e t t l i n g s h o u l d be p r e v e n t e d . Double r e i n f o r c e m e n t i n c r e a s e s t h e r e s i s t a n c e t o c r a c k i n g , b u t i s n o r m a l l y n o t necessary and cannot be used as an a l t e r n a t i v e t o p r e v e n t i o n o f s e t t l i n g . - V e n t i l a t i o n o f t h e b u i l d i n g should provide a reasonable v e n t i l a t i o n r a t e and t h e n e g a t i v e p r e s s u r e i n d o o r s s h o u l d be minimized. A b a l a n c e d v e n t i l a t i o n system w i t h s u p p l y and exhaust v e n t i l a t i o n i s t o be p r e f e r r e d t o a mechanical exhaust v e n t i l a t i o n system. - M i n i m i z e t h e c o n t a c t between l i v i n g a r e a and s u b j a c e n t s o i l . B u i l d i n g s w i t h s l a b on grade o r v e n t i l a t e d c r a w l space r e q u i r e l e s s m o d i f i c a t i o n o f t h e s t a n d a r d d e s i g n than houses w i t h b a s e ments. I f basements cannot be a v o i d e d on radon dangerous s o i l , i t i s recommended t o keep t h e basement s e p a r a t e d from t h e l i v i n g space by n o r m a l l y c l o s e d doors and i f p o s s i b l e , i n s t a l l exhaust v e n t i l a t i o n from t h e basement. - Avoid b u i l d i n g blocks w i t h interconnected i n t e r n a l c a v i t i e s i n basement w a l l s . Basement w a l l s made from i n s i t u (poured) c o n c r e t e a r e recommended. Concrete elements r e q u i r e c a r e f u l and permanent s e a l i n g o f a l l j o i n t s . Designs s i m i l a r t o swimming p o o l s , manure t a n k s i n a g r i c u l t u r e and bomb s h e l t e r s w i l l p r o v i d e a radon s a f e c o n s t r u c t i o n . - I f p o s s i b l e , make t h e c o n s t r u c t i o n f o r g i v i n g t o l a t e r a p p e a r i n g c r a c k s i n t h e c o n c r e t e . I f a s l a b i s covered w i t h a permanently e l a s t i c m a t e r i a l , l i k e r u b b e r i z e d a s p h a l t o r bitumen, f u t u r e cracks i n the concrete w i l l not a u t o m a t i c a l l y r e s u l t i n a route o f e n t r y f o r s o i l radon. - Prepare i n t h e d e s i g n stage f o r an easy remedy i n case t h e passive precautions f a i l . T h i s i s an i m p o r t a n t component i n a c o s t - e f f e c t i v e s t r a t e g y . A m b i t i o u s p r e c a u t i o n s g i v i n g low radon c o n c e n t r a t i o n i n 100% o f t h e new b u i l d i n g s w i t h o u t any r e t r o f i t m o d i f i c a t i o n s w i l l g i v e a h i g h e r t o t a l c o s t . An a c c e s s i b l e and


528

R A D O N AND ITS DECAY PRODUCTS


v e n t i l a t e d c r a w l space between t h e l i v i n g space and t h e s o i l w i l l always p r o v i d e p o s s i b i l i t i e s f o r v a r i o u s r e m e d i e s . D e p r e s s u r i z a t i o n and/or v e n t i l a t i o n o f t h e c a p i l l a r y b r e a k i n g l a y e r has been proven t o be an e f f e c t i v e r e m e d i a l a c t i o n ( E r i c s o n and Schmied, 1984). P r e i n s t a l l a t i o n o f a duct from t h e c a p i l l a r y b r e a k i n g l a y e r t o t h e atmosphere o r by p l a c i n g d r a i n pipes f o r future d i s t r i b u t i o n of negative pressure i n t h e c a p i l l a r y b r e a k i n g l a y e r by s u c t i o n a t one p o i n t p r o v i d e p o s s i b i l i t i e s f o r e f f e c t i v e remedies. A i r from c r a w l space o r s u b j a c e n t s o i l can be v e r y r i c h i n radon and s h o u l d n o t be mixed w i t h exhaust a i r and p o s s i b l y mixed w i t h s u p p l y a i r i n a h e a t exchanger. W i t h m o d i f i c a t i o n s a c c o r d i n g t o t h e above p r i n c i p l e s i t i s p o s s i b l e t o develop any s i t e and s t i l l keep a c c e p t a b l e c o n c e n t r a t i o n s o f radon i n t h e d w e l l i n g s . P r o b a b l y t h e same p r i n c i p l e s a r e a p p l i c a b l e a l s o i n c o n s t r u c t i o n on o l d waste dumps p r e v e n t i n g i n f i l t r a t i o n o f o t h e r gases, f o r example methane o r mercury vapor. F i g u r e s 1 and 2 p r e s e n t two examples o f radon s a f e d e s i g n s w h i c h i n most cases can be regarded as o v e r l y s a f e . These two p a r t i c u l a r b u i l d i n g s were e r e c t e d i n t h e v i l l a g e o f Varnhem where t h e s o i l i s permeable g r a v e l c o n t a i n i n g alum s h a l e w i t h an e l e v a t e d a c t i v i t y o f uranium. The radon c o n c e n t r a t i o n i n t h e s o i l gas i s between 100,000 and 300,000 Bq/m . The f i r s t one i s p r o v i d e d w i t h a m o n l i t h i c c o n c r e t e s l a b i n t h e c r a w l space. The s l a b and f o u n d a t i o n a r e covered w i t h r u b b e r i z e d a s p h a l t . The c r a w l space i s v e n t i l a t e d by n a t u r a l draught s e p a r a t e l y from t h e v e n t i l a t i o n o f t h e d w e l l i n g . The c o n c e n t r a t i o n o f radon i n t h e c a p i l l a r y b r e a k i n g l a y e r has been measured s e v e r a l times w i t h r e s u l t s r a n g i n g from 122,000 t o 340,000 Bq/m . Four measurements w i t h i n t h e c r a w l space have ranged from 70 t o 240 Bq/m . The o t h e r house has c o n c r e t e s l a b s between t h e f o o t i n g s i n t h e c r a w l space and t h e c r a w l space i s v e n t i l a t e d as an i n t e g r a l p a r t o f t h e s u p p l y exhaust v e n t i l a t i o n system o f t h e l i v i n g space. Three measurements have g i v e n 55 t o 75 Bq/m i n t h e l i v i n g space. The m o d i f i c a t i o n s i n d e s i g n added a p p r o x i m a t e l y 4% t o t h e b u i l d i n g c o s t s . As a c o n t r a d i c t i o n t o t h e above examples i s a h y p o t h e t i c a l house d e s i g n e d t o maximize t h e r i s k f o r i n f i l t r a t i o n o f s o i l r a d o n . The house has a f u r n i s h e d basement i n open c o n t a c t w i t h t h e main l i v i n g space. The basement s l a b i s poured between t h e f o o t i n g s w i t h o u t s e a l i n g t h e j o i n t s between basement w a l l s and s l a b . The basement w a l l s a r e made from b u i l d i n g b l o c k s h a v i n g i n t e r c o n n e c t e d i n t e r v a l c a v i t i e s . The v e n t i l a t i o n i s o f t h e m e c h a n i c a l exhaust t y p e w i t h o u t a i r i n l e t s , thus c r e a t i n g a strong negative pressure indoors a t a f a i r l y low a i r exchange r a t e . These a r e common c h a r a c t e r i s t i c s i n t h e e x i s t i n g b u i l d i n g s t o c k . I f surrounded by permeable s o i l such b u i l d i n g s o f t e n f a c e an i n f i l t r a t i o n o f s o i l gas e q u a l t o 0.1 t o 5% o f t h e t o t a l a i r exchange r a t e . T h i s means t h a t t h e i n f i l t r a t i n g s o i l gas i s d i l u t e d 20 t o 1000 times w i t h outdoor a i r i n f i l t r a t i n g through l e a k s above ground l e v e l . I f t h e c o n c e n t r a t i o n o f radon i n t h e s o i l gas i s 100.000 Bq/m t h e c o n t r i b u t i o n t o i n d o o r radon o f t e n i s 100 t o 5000 Bq/m . There i s no c o n f l i c t between energy c o n s e r v a t i o n and radon p r o t e c t i v e o r s a f e d e s i g n . Radon s a f e c o n s t r u c t i o n can be made as energy e f f i c i e n t as can c o n v e n t i o n a l d e s i g n . Radon s a f e d e s i g n o n l y 3

3

3

3

3

3


ERICSON AND

SCHMIED



38.

F i g u r e 2. Radon p r o t e c t i v e d e s i g n ; c r a w l space p r o v i d e d w i t h a s l a b , m e c h a n i c a l s u p p l y exhaust v e n t i l a t i o n o f l i v i n g space and c r a w l space.


529

RADON AND ITS DECAY PRODUCTS


530

i n t r o d u c e s some r e s t r i c t i o n s on how t o c o n s e r v e energy. Energy c o n s e r v a t i o n by i n c r e a s e d t i g h t n e s s o f t h e b u i l d i n g and v e r y low a i r exchange r a t e s must be d i s c o u r a g e d due t o i t s e f f e c t on i n d o o r a i r q u a l i t y and h u m i d i t y even w i t h o u t r e g a r d t o r a d o n . W i t h m e c h a n i c a l v e n t i l a t i o n systems i n s t a l l e d , heat r e c o v e r y w i l l pay i t s own c o s t s i n temperate c l i m a t e s . I n o r d e r t o a v o i d s t r o n g n e g a t i v e p r e s s u r e i n d o o r s , heat exchangers w i t h balanced v e n t i l a t i o n a r e t o be p r e f e r r e d f o r exhaust v e n t i l a t i o n w i t h a h e a t pump f o r r e c o v e r i n g the heat. Every m o d i f i c a t i o n i n d e s i g n , as w e l l as r e m e d i a l a c t i o n s , must be made a f t e r due c o n s i d e r a t i o n o f b u i l d i n g p h y s i c s . O t h e r w i s e negative s i d e e f f e c t s can occur. Examples a r e l o c a l l y h i g h r e l a t i v e h u m i d i t y i n a i r , c o n d e n s a t i o n o f m o i s t u r e and development o f mold. W i t h due c o n s i d e r a t i o n t o t h e c o n s t r a i n t s l a i d by b u i l d i n g p h y s i c s , however, m o d i f i c a t i o n s t o radon s a f e d e s i g n can g i v e p o s i t i v e t r a d e o f f s as reduced p o s s i b i l i t y f o r m o i s t u r e t r a n s p o r t and development o f mold. Monolithic

Slabs

I n t h e same v i l l a g e as t h e p r e v i o u s two examples, a group o f 21 twos t o r y , wood frame d w e l l i n g s were b u i l t i n 1979-80. The houses were founded w i t h m o n o l i t h i c s l a b s ( F i g u r e 3 ) . A l a y e r o f f i n e g r a i n e d moraine was p l a c e d under t h e c a p i l l a r y b r e a k i n g l a y e r i n o r d e r t o r e s t r i c t t h e f l o w o f s o i l gas t o t h e b u i l d i n g from t h e s u b j a c e n t g r a v e l . The v e n t i l a t i o n systems a r e o f t h e b a l a n c e d s u p p l y exhaust type w i t h v a r i a b l e speed and heat exchanger. As an attempt t o i n c r e a s e t h e t i g h t n e s s o f t h e f o u n d a t i o n , aluminum f o i l l a m i n a t e d w i t h p o l y e t h y l e n e and p o l y e s t e r was a p p l i e d above t h e s l a b i n 11 houses. I n t h r e e houses, t h e f o i l was j o i n e d by w e l d i n g t h e p o l y e t h y l e n e and i n t h e o t h e r seven by o v e r l a p p i n g j o i n t s . Measurements have been performed f o u r t i m e s from 1980 t o 1985. I t has not, however, been p o s s i b l e t o d e t e c t any e f f e c t o f t h e aluminum f o i l . Thus, t h e s l a b i t s e l f has p r o v i d e d enough t i g h t n e s s . The r e s u l t s a r e p r e s e n t e d i n T a b l e I . I n most o f t h e houses, t h e radon c o n c e n t r a t i o n i s l e s s than 200 Bq/nr. A few o f t h e houses have h i g h e r c o n c e n t r a t i o n s i n d i c a t i n g some i n f i l t r a t i o n o f s o i l gas. A contributionof 100 t o 500 Bq/m i n d i c a t e t h a t t h e i n f i l t r a t i n g s o i l gas, w i t h 200,000 t o 300,000 Bq/ra , i s d i l u t e d 500-2000 t i m e s . I f the m e c h a n i c a l v e n t i l a t i o n systems a r e operated a t a c a p a c i t y o f 200 n r v h , t h e i n f i l t r a t i o n i n t h e s e houses would be 0.1 t o 0.4 n r / h o f s o i l gas. The e l e v a t e d l e v e l s have been measured i n t h e same houses every time and i n t h e m a j o r i t y o f t h e houses n o t h i n g b u t low concen t r a t i o n s have been measured. The m o d i f i c a t i o n s i n d e s i g n added n o t more than 1% t o t h e b u i l d i n g c o s t s . As an a l t e r n a t i v e t h e s l a b s c o u l d have been covered w i t h r u b b e r i z e d a s p h a l t , e s p e c i a l l y near e n t e r i n g u t i l i t i e s , and t h e s t r u c t u r e s prepared f o r an easy r e t r o f i t w i t h mecahnical v e n t i l a t i o n o r d e p r e s s u r i z a t i o n o f t h e c a p i l l a r y b r e a k i n g l a y e r t o be used i n t h e few b u i l d i n g s where radon i n f i l t r a t e s . W i t h t h i s s t r a t e g y i t i s assumed t h a t a l l houses c o u l d have been under 200 Bq/m a t an added b u i l d i n g c o s t o f a p p r o x i m a t e l y 0.5%. In t h e town o f Ljungsbro 27, 1 1 / 2 - s t o r y , wood frame d w e l l i n g s w i t h o u t basements were b u i l t on m o n o l i t h i c s l a b s . V e n t i l a t i o n i s p r o v i d e d by a duct system connected t o an exhaust f a n . I n t h e s u b 3

3

3



38.

ERICSON AND SCHMIED


531

Figure 3. Mechanically ventilated wood frame dwelling with monol i t h i c slab.

Table I.

Radon Concentration

Distribution of Measured Radon Concentration, Bq/m , in 21 Detached Houses Designed According to Figure 3

f

Dec 80 -

0-50 50-100 100-150 150-200 200-250 250-300 300-350 350-400 400-450 450-500 500-550 550-600 600-650

1 5 5 3 1 1 2

Jan «81*

Feb '81**

2 5 2 3 1 1 2 1

Summer »82*

8 3 1 2

Spring '85***

1 3 4 4 2 1 1 1

1 1

1

900-950 1200-1250

1 1

* 30 days average ** grab samples *** 3 months average



532

j a c e n t s o i l , radon c o n c e n t r a t i o n s r a n g i n g from 10,000 t o 211,000 Bq/m were measured. Together w i t h t h e upper l a y e r o f t h e ground b e i n g permeable g r a v e l and sand, radon p r o t e c t i v e d e s i g n was i n d i c a t e d . I n order t o get a passive v e n t i l a t i o n o f t h e subjacent s o i l , p e r f o r a t e d d u c t s were i n s t a l l e d i n t h e c a p i l l a r y b r e a k i n g l a y e r w i t h c o n t a c t t o t h e atmosphere through t h e edge beam on both s i d e s o f the houses ( F i g u r e 4 ) . R e s u l t s from measurements made i n 1981, 1982 and 1985 a r e p r e s e n t e d i n T a b l e I I . I n t h e m a j o r i t y o f t h e houses, t h e r e i s no s i g n o f i n f i l t r a t i o n o f s o i l gas. D u r i n g t h e 1982 measu rements, t h e d u c t s i n t h e c a p i l l a r y b r e a k i n g l a y e r were s e a l e d i n 10 and open i n 17 houses. The houses w i t h s e a l e d d u c t s d i d n o t have h i g h e r radon c o n c e n t r a t i o n s , i n d i c a t i n g t h a t t h e m o n o l i t h i c s l a b p r e v e n t s i n f i l t r a t i o n o f s o i l gas, though t h e m e c h a n i c a l exhaust v e n t i l a t i o n provides a constant negative pressure i n t h e b u i l d i n g s .


3

T a b l e I I . D i s t r i b u t i o n o f Measured Radon C o n c e n t r a t i o n , Bq/m , i n 27 Detached Houses Designed A c c o r d i n g t o F i g u r e 4

Radon, Bq/m

3

0-50 50-100 100-150 150-200 200-250 250-300 300-350

1981

1982

5 2

24 1 1

1985

9 8 2 3 1

1

V e n t i l a t e d Crawl Space B u i l d i n g s w i t h v e n t i l a t e d c r a w l space a r e i n h e r e n t l y radon p r o t e c tive. I n one w i d e l y used d e s i g n , t h e c r a w l space i s m e c h a n i c a l l y v e n t i l a t e d by t h e exhaust a i r from t h e l i v i n g space ( F i g u r e 5 ) . T h i s d e s i g n p r e s e n t s t h e advantage t h a t t h e h e a t i n t h e exhaust a i r i s used t o p r o v i d e a warm f l o o r i n t h e l i v i n g space. R e c e n t l y more h e a t i s o f t e n e x t r a c t e d from t h e exhaust a i r a f t e r i t h a s passed t h r o u g h the c r a w l space. I f t h e a i r i s contaminated w i t h radon i n t h e c r a w l s p a c e , t h i s i s p r e f e r e n t i a l l y done by a h e a t pump. I f h e a t i s t r a n s f e r r e d t o t h e s u p p l y a i r i n an a i r t o a i r heat exchanger c o n t a m i n a t i o n o f t h e s u p p l y a i r s h o u l d be a v o i d e d . Thus, t h e p r e s s u r e d i f f e r e n t i a l between t h e s u p p l y and exhaust a i r and t h e t i g h t n e s s o f t h e h e a t exchanger h a s t o be c a r e f u l l y c o n s i d e r e d . We have seen an example where radon i n t h e exhaust a i r from t h e c r a w l space contaminated t h e s u p p l y a i r w i t h 600 t o 800 Bq/m o f radon. I f the p r e s s u r e i n t h e c r a w l space i s lower than i n t h e l i v i n g s p a c e , the radon c o n c e n t r a t i o n i n t h e c r a w l space can be v e r y h i g h w i t h o u t any s u b s t a n t i a l t r a n s p o r t i n t o t h e l i v i n g s p a c e . I f t h e p r e s s u r e i n the c r a w l space i s h i g h e r than o u t d o o r s , i n f i l t r a t i o n o f s o i l radon 3





533

Figure 4. Mechanically ventilated wood frame dwelling on a monol i t h i c slab, natural draught v e n t i l a t i o n of the c a p i l l a r y breaking layer by ducts through the edge beam.

Figure 5.

Mechanical exhaust v e n t i l a t i o n through the crawl space.



534

i n t o t h e c r a w l space i s c o u n t e r a c t e d e f f i c i e n t l y and t h e radon c o n c e n t r a t i o n i n t h e a i r from t h e c r a w l space c a n t h e n be s u r p r i s i n g l y low, even on l a n d where radon o f t e n i n f i l t r a t e s i n t o conventional buildings. In 24 d w e l l i n g s w i t h exhaust a i r v e n t i l a t e d c r a w l space, we have measured t h e radon c o n c e n t r a t i o n i n 1982 and 1985. The r e s u l t s a r e p r e s e n t e d i n T a b l e I I I . With few e x c e p t i o n s t h e radon c o n c e n t r a t i o n s have been low. The anomalously h i g h v a l u e from 1982 has been e x p l a i n e d by c o n t a m i n a t i o n o f t h e s u p p l y a i r i n a heat exchanger. The o t h e r h i g h v a l u e was measured i n a house w i t h o u t a h e a t exchanger and i n which we measured o n l y 25 Bq/m i n 1982. The c o n c e n t r a t i o n i n t h e c r a w l space was h i g h , 4600 Bq/m . I n T a b l e IV, measurements i n s i x d w e l l i n g s w i t h a s p h a l t p a i n t e d 3


3

T a b l e I I I . D i s t r i b u t i o n o f Measured Radon C o n c e n t r a t i o n i n 24 Detached Houses Designed w i t h M e c h a n i c a l Exhaust V e n t i l a t i o n t h r o u g h t h e C r a w l Space

Radon, Bq/nr

1982*

1985

0-50 50-100 100-150 150-200 200-250 250-300 300-350

13 5 1

7 7 7 1 1

1 1

900-950

* Measurements performed i n 20 houses. T a b l e IV. C o n c e n t r a t i o n o f Radon i n Indoor A i r i n 6 Detached Houses P r o v i d e d w i t h A s p h a l t Coated S l a b i n t h e C r a w l Space

Measured Radon C o n c e n t r a t i o n , Bq/m House

1982

1985

1 2 3 4 5 6

10 10 10 10 10 15

50 100 100 140 50 20



535 Modified Design Prevents Infiltration

slab in the crawl space are presented. These houses have natural draught ventilation through air inlets in the foundation walls only or through air inlets and a duct over the roof. The radon concen tration in the soil gas under these houses range from 40,000 to 100,000 Bq/m. The increase in values from 1982 to 1985 can possibly be attributable to inaccuracy in the detectors used. Literature Cited


3

Central Management and Housing Corporation, Canada, Technical Memorandum 33/79 (1979). Ericson, S.-O. and H. Schmied, Modified Technology in New Construc tions and Cost-Effective Remedial Action in Existing Structures to Prevent Infiltration of Soil Gas Carrying Radon. In Proceedings of the 3rd International Conference on Indoor Air Quality and Climate, Stockholm, 5:153-158 (1984). RECEIVED October 27, 1986


Radon and Its Decay Products - American Chemical Society

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