I bought a BX700UI APC UPS for my linux arm server setup (40 watts) to protect it from power cut. - I have the server in the bedroom is it dangerous to have such an Ups in a small bedroom? - Thinking of gases?

  • \$\begingroup\$ Yes probably, If bedroom has no windows that are opened regularly. But it's not like the battery will spew hydrogen willy nilly. \$\endgroup\$
    – Indraneel
    Jan 12, 2019 at 20:18
  • \$\begingroup\$ @Indraneel To quote another user "That's hardly an answer, without hard data." How can you say that it is dangerous? Remember, "This is an EE site after all, we all need numbers!" \$\endgroup\$ Jan 12, 2019 at 21:08

2 Answers 2


Valve regulated lead acid (VRLA) batteries and modular battery cartridges (MBC) do not require special battery rooms and are suitable for use in an office environment. Air changes designed for human occupancy normally exceed the requirements for VRLA and MBC ventilation.


Also there is a little known fact that Hydrogen will not explode with O2 unless it exceeds the lower explosive level, LEL concentration of 4%, then the probability rise above 0% at this threshold with a spark.

Compare generation of volume of gas from a faulty battery and faulty OVP and failed charger safety ( triple-mode failure).

background and my logic

How much gas volume can an SLA battery generate compared to humans breathing out toxic carbon monoxide (CO)? not much.

Yet a vented lead acid battery, which can generate 60x more than a SLA is unsafe, if overcharged .

For a small bedroom, this would need a lot of batteries to generate 4% H2 from overcharge failures and H2 generation, given convection flow of air needed for humans to not asphyxiate from CO breathing. An SLA battery is unlikely to create this amount of H2 with a battery fault compared to the flow of CO from breathing out. It may also trigger UPS battery fail alarm if this condition were detected.

  • \$\begingroup\$ I'm not a geek but is it a "Valve regulated lead acid" that is in my ups? - apc.com/shop/my/en/products/… \$\endgroup\$ Jan 12, 2019 at 20:28
  • \$\begingroup\$ @ReneMortensen Yes, I believe so. My UPS had the battery installed on its side, so it is also probably a gel or mat. The cheapest SLA (with valve) are in the small cheap 4V batteries in rechargeable flashlights etc. It may be wise to keep them properly oriented during charging. I've never had one leak, but I don't know if they are gel/mat based too. You can see the valve on the top, sometimes. \$\endgroup\$
    – Indraneel
    Jan 12, 2019 at 20:40
  • \$\begingroup\$ So in general it's not dangerous to use in a bedroom as i understand? :) \$\endgroup\$ Jan 12, 2019 at 20:49
  • \$\begingroup\$ Correct. If air flow is safe for humans , SLA's won't make it unsafe. yet not so for Flooded cell types. \$\endgroup\$ Jan 12, 2019 at 20:57
  • \$\begingroup\$ @ReneMortensen No, that interpretation is not right. The valve exists to prevent explosion, not to prevent H2 from escaping. Actually, the valve exists to allow H2 to escape and prevent explosion. How much H2 depends on acid and charging stuff. As I said, we need numbers to quantify all that. \$\endgroup\$
    – Indraneel
    Jan 12, 2019 at 21:22

In normal operation it should not emit any gasses, the sealed lead acid batteries may occasionally vent a very small quantity of hydrogen during charging, but so does your digestive tract.

  • \$\begingroup\$ That's hardly an answer, without hard data. \$\endgroup\$
    – Indraneel
    Jan 12, 2019 at 20:19
  • \$\begingroup\$ I also do not assume that Ups charges more when it is fully charged once unless power is interrupted? - But maybe it is designed to discharge and charge the battery? \$\endgroup\$ Jan 12, 2019 at 20:20
  • \$\begingroup\$ @ReneMortensen I doubt it. What would happen if there is a power outage while the UPS was discharging the battery? \$\endgroup\$
    – Indraneel
    Jan 12, 2019 at 20:22
  • \$\begingroup\$ What data do you need Indraneel ? apc.com/shop/my/en/products/… \$\endgroup\$ Jan 12, 2019 at 20:24
  • \$\begingroup\$ I open the window in the room daily when I go to the bath to vent out as the bathroom is at the end of the room :) - But don't know if that is enough? \$\endgroup\$ Jan 12, 2019 at 20:26

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