I would love return of fresh air stock particularly as someone who suffers from sinus problems and finds air conditioning unbearable at times. However, doubt many would agree with me.
The aircon stock we have constantly filters the air and replaces the air with fresh air from outside every 7-10 minutes (depending on class). I believe other stock is very similar. Given the benefits of modern HVAC over opening windows I'm not sure why you'd want to go back.
So are you suggesting that trains should have 'permanently open' windows or louvres, even in winter? A sort of 'mobile bus shelter' concept to ensure continuous ample ventilation?
With regards to germs, this I think is only an issue if the air is continually recirculated. However if the air conditioning continually brings in new air from outside I don’t think this is an issue.
Yes, the Mark 2/2a/2b and 2c stock vehicles were equipped with pressure ventilation - as well as opening windows. The Mark 2c stock was built with lowered cielings for the eventual retro-fitting of air conditioning equipment but, in the end, it never happened. Mark 2d/2e/2f/3/4 and 5 vehicles were fitted with air-con from new.
Strictly speaking the 2D and 2E are pressure ventilated as well but with an air-con system provided in addition; essentially what would've happened with the 2C if air-con had been retro-fitted.
If by "summer" you mean "when it's hot" then passengers get very uncomfortable. (I recall Shrewsbury-Crewe via Chester on a 158 with failed air-con where we are all uncomfortable, and a poor baby was in genuine distress) But non air-con stock could also get very hot and sticky in hot weather.
Haven't nearly all intercity trains been air conditioned for at least 35 years?
No.
I believe so, probably longer.
Mk2D stock entered service in April 1971 giving First and Second Class passengers on the ECML non-supplement air-con travel, by 1975 and the introduction of Mk3s on the WCML, most front line InterCity trains on the WCML, ECML and GWML were air-con. Though some secondary services particularly on the LMR and WR remained pressure ventilated Mk2s as did all the Inter-Regional trains until the HSTs enabled large scale cascading of Mk2 air-cons to those services.
Essentially I guess they did for mainstream workings once the HSTs were available but I travelled on the 1820 London Paddington to Hereford as far as Reading on 12 October 1991 formed of a 47 and what appears to have been a short formation of Mark 1 charter stock with first class in air conditioned carriages so some non air-conditioned stock could still be used when necessary later than 1989.
This is a myth. During the height of the pandemic in the US there were still plenty of flights operating and the spread of Covid was monitored. It was found that aircraft are in fact one of the safest places to be as far as the spreading of infections in socially mixed environments goes. What can make them seem unhealthy is the pressurisation of the cabin to an equivalent height well above sea-level, though to an absolute maximum of 8,000 feet, which can be uncomfortable to those with certain pre-existing conditions as well as necessarily having a low humidity. In fact I would suggest it is the reduced humidity of a typical air-conditioned environment that can make it feel unhealthy. Simple answer is to maintain personal hydration, indeed that is standard advice for long-haul aircraft passengers.
OK, how about excluding the RMBs, which were a bit of a special case in the absence of sufficient catering vehicles?
Modern air conditioning tends not to break down. Ignoring 158s and 166s it tends to be fairly reliable. The problem even with staff controlled opening windows is that they get opened before the air conditioning has actually malfunctioned. Windows that can only be opened by a trained fitter might be admissible.
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