This enables them to tell customers that if they wish to have the house checked for radon and if it is found to be affected, they can easily modify the passive system by means of a small fan in order almost certainly to reduce the levels significantly.

In the United States, there are three distinct sets of building codes and to some extent these are applied in different regions.

The Standard Code (The Southern Standard Building Code) has more emphasis on wind loading because it is used primarily in the parts of the US where storms are more prevalent.

The Uniform Building Code (International Conference of Building Officials) and the National Building Code (BOCA or Building Officials and Code Administrators) have emphasis on snow loads for the northern states and on seismic or building structure provisions for use in the western USA.

For one and two family dwellings, there is a fourth code which is subscribed to by the other three and represents essentially the only nationally accepted Building Code. There is a great deal of overlap between the provisions of these Codes, but there are differences.

A house in many regions may be constructed to one or another of the Codes depending much upon the preferences of the local building inspectors. Building inspection in some States is closely controlled, in other States is haphazard. Often this is a problem of staffing levels.

In the more outlying districts it is generally three years before Code requirements are widely enacted and it may be fifteen years before there is full implementation of building changes because inspectors have wide discretion, and there are usually let-out clauses within at least the first drafts of additions to any Code to allow for local discretion and for particular building practices.

EPA are working on a proposed Model Standard for new houses which could be considered for adoption by all the County and State bodies. However, there is no prospect of EPA being able to regulate across the United States for radon, no matter how much they might wish to do so. The Model Code that was published in draft form (for comment) is intended for use by code development organisations, States and local jurisdictions as they develop and enforce their local building codes. To some extent the EPA draft will be like the old Model Water Bye-laws in the UK with many parts being widely adopted but with freedom to implement local preferences.

It is often said that about 25% of the houses in the United States may have elevated radon levels; this may be owing to reliance on basement radon measurements and the true figure may be nearer to 7 or 8% based upon radon levels in the principal inhabited rooms.

There are around 60 million single family residences in the USA together with about 20 million apartments, giving a total of around 80 million. The build rate is traditionally around 1 million per year but seems likely to be below this for the next few years because of a recession.

The EPA will be delineating Counties and States within the US on the basis of expected radon levels in typical dwellings based very much upon geology and a knowledge of radon levels already found within existing dwellings. This is similar to the UK scheme, but see Section 54.

Within what are called Priority 1 areas it is envisaged that active systems will be required (but this does not mean that any County need abide by this ruling). The proposed Code will be a prescriptive standard but with no need for checking of radon levels after construction: it will simply be assumed that the active system will work adequately to reduce the radon levels to a very low value. If systems are installed correctly there is little reason to doubt this.

Within these Priority 1 areas (areas in which houses have above 75 Bq/m³ in the living areas on average, and therefore broadly equivalent to Devon) would be delineated hot-spot areas in which houses were known to average over 150 Bq/m³. No further requirements are envisaged in these areas, but they may be highlighted on the EPA colour coded maps and local officials encouraged to give particular attention to radon measures.

Within Priority 2 areas there will be no requirement to install active systems in new houses. However, there will be provision for testing of the passive systems (by monitoring indoor levels). Builders will be required to install a fan and (presumably) to re-test the system if levels are high.

In the Model Code the liability of the builder and local building officials will terminate at the end of these stages whether or not the indoor radon levels are low.

There is some discussion as to whether the prescriptive approach within the Priority 1 areas is correct because it may result in the installation of tens of thousands of fans in dwellings where they were not really necessary - because a passive system might have produced radon concentrations at an acceptable level.

The danger is that it may become a part of folklore that radon fans are often not necessary. Then the temptation may be not to operate them in all homes.

There is some support for the view that fans should only be installed where required, and with the possible long term advantage that people will come to associate them with a genuine need.

However, up to 100,000 houses may be constructed every year with radon fans simply because they are within Priority 1 areas. (This approach is favoured by fan manufacturers.)

EPA have undertaken cost-benefit analysis in respect of new build radon resistant construction. In some schemes, the installed cost of all the measures is only $200 to $400 per house.

A figure of $140,000 per life saved has resulted from some studies, but needs to be multiplied by a factor of at least 4 to give the non-smoker cost-benefit. The costs are then within the normal range of $300,000 to $9M per life saved that EPA have suggested that the public is willing to pay to reduce risks. It would be interesting to relate this to health costs and benefits in the USA: it has been reported that that the Office of Management and Budget calculated the benefit of some EPA rules to be as extreme as $57 trillion per life saved!

Another interesting statistic is that EPA claim around 140 lives saved per year from one million new houses built to radon proof standards. Thus, were the entire housing stock of Devon and Cornwall (about 700,000) to be replaced by radon resistant construction (an assuming roughly equal average commencing radon levels) then perhaps around 80 lives per year could be prolonged, including around 15 to 20 non smokers.

Proper calculations need to consider realised average radon levels with and without radon resistant construction.

Despite the emphasis within the EPA guidance on passive stack vents (so as to avoid undue use of fans) there is little evidence as yet of system effectiveness. This is being addressed under several research programs, but some have suffered cutbacks owing to lack of State funding. (see Section 63).

In what seems an act of marketing desperation, some radon reduction packages are being 'sold' on the basis of their providing better energy standards, because of the sealing work that is being undertaken. However, this may not be necessary for successful operation of passive and active systems.

Another way of selling the benefits of radon resistant construction is to claim that better fire resistance results - from the stopping up of gaps between ground and first floor levels. However, installation of a plastic pipe through a ceiling and without use of a fire damper would introduce an extra route for flame and smoke. This is not an idle point: in New Jersey a fatality occurred recently in a house known to the author and fitted with a radon system. Smouldering papers in the basement caught alight, the smoke detectors failed to work, the plastic pipes melted and the owner was asphyxiated. The radon system was not implicated as a prime cause of death.

There is considerable emphasis within the draft Code on construction methods to minimise pathways for soil gas to enter, reducing or negating any pressure differentials between indoors and outdoors, and on care in selection and use of HVAC systems. The guidance is in general terms only.

It is stressed that the EPA Model Code is only the basis for developing building codes for radon resistant construction that are appropriate to particular localities, and that these must be developed and implemented by Counties and States having jurisdiction.

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